(1) Everett asked:
In "On Sense and Nominatum," Gottlob Frege writes not only of reference but also of sense as forming the objective basis that underlies meaning. (There is also a subjective aspect, called tone, but Frege does not give it much credence.) In the essay, Frege tantalizingly hints that the ability to develop alternate senses for some particular reference is a source for creative thought about that reference ... i.e. of imagining the reference in a different way. wondering whether any philosopher has taken up the task of refining the concept of sense so that the roll sense plays in the make up of creativity is made clear. Just because I haven't seen anything which delves the question in-depth doesn't mean it isn't out there. Or perhaps you think my question is faulty, ill-posed or nonsense? Any response would be cheerfully accepted.
I think your question is very rambling. However, what I think you want are references to philosophical works on creativity, especially from the analytic tradition, right? I don't know too many; here are a few:
Crawford, D. W. 1982. Kant's theory of creative imagination, edited by T. Cohen and P. Guyer. Chicago, IL: The University of Chicago Press.
Johnson, M. 1985. Imagination in moral judgment. Philosophy and Phenomenological Research 46 (2):265-280. ------. 1987. The body in the mind. Chicago, IL: University of Chicago Press.
Minnameier, G. 2004. Peirce-Suit of Truth Why Inference to the Best Explanation and Abduction ought not to be Confused. Erkenntnis 60:75-105.
Turner, M., and G. Fauconnier. 1999. A mechanism of creativity. Poetics Today 20 (3):397-418.
Dastani, M., B. Indurkhya, and R. Scha. 2003. Analogical projection in pattern perception. Journal of Experimental & Theoretical Artificial Intelligence 15 (4):489-511.
Fields, C. 2004. The role of aesthetics in problem solving: some observations and a manifesto. Journal of Experimental & Theoretical Artificial Intelligence 16 (1):41-55.
Goodman, N. 1976. Languages of art. 2-d ed. Indianapolis, IN: Hackett Publishing Company.
------. 1988. Ways of worldmaking. 5th ed. Indianapolis, IN: Hackett Publishing Company.
Scruton, R. 1987. Analytical philosophy and the meaning of music. The Journal of Aesthetics and Art Criticism 46:169-176.
Silveira, L.F.B. da. Some considerations about semiotic machines from the point of view of Charles S. Peirce's Philosophy [http://www.inm.de/kip/SEMIOTIC/silveira_article.html].
Steven Ravett Brown
(32) Peter asked:
How much is reality mathematical?
We don't know. Mathematics is a way we model the world. How successfully do our models function, how close is their structure to the structure of reality... these and related issues are questions that have been debated for millennia, and are still being debated.
You might try these:
Boole, G. 1958. An investigation of the laws of thought. 2-d ed. New York, NY: Dover Publications.
Dipert, R.R. 1997. The mathematical structure of the world: the world as graph. The Journal of Philosophy 94 (7):329-358.
Eisenbud, L. 1971. The conceptual foundations of quantum mechanics. Edited by W. C. Michels, Van Nostrand Reinhold Momentum Books. New York, NY: Van Nostrand Reinhold Company.
Godel, K. 1992. On formally undecidable propositions of Principia mathematica and related systems. Translated by B. Meltzer and R. B. Braithwaite. Mineola, NY: Dover Publications, Inc. Original edition, 1962.
Lakoff, G., and R.E. Nunez. 2000. Where mathematics comes from: how the embodied mind brings mathematics into being. New York, NY: Basic Books.
Nagel, E., and J. R. Newman. 1958. Godel's proof. New York, NY: New York University Press.
Narens, L. 2002. The Irony of Measurement by Subjective Estimations. Journal of Mathematical Psychology 46:769-788.
------. 2002. A Meaningful Justification for the Representational Theory of Measurement. Journal of Mathematical Psychology 46:746-768.
Null, G.T., and R.A. Simons. 1981. Aron Gurwitsch's ordinal foundation of mathematics and the problem of formalizing ideational abstraction. Journal of the British Society for Phenomenology 12 (2):164-174.
Shepard, R. 1964. Attention and the metric structure of the stimulus space. Journal of Mathematical Psychology 1:54-87.
Steven Ravett Brown
(47) Andreas asked:
I am after a proper explanation of the term "non-trivial" as used in scientific and philosophical papers. I am aware that the term is used in mathematics and particularly in probability; but what I am asking about is what does it really mean when people say "the results of such and such a study are non-trivial; or in an article on consciousness, "when we talk about consciousness is an unavoidable and non-trivial part of trying to understand the relation between consciousness and intentionality"
This is quite an interesting question, and as far as I know there's no really good answer to it. Here's one take on it: to really be able to master a field of study, anything, really, ranging from carpentry to cab-driving to mathematics to philosophy, and so forth, requires about 5-10 years of concentration for most people. Now, given that (and that's actually been fairly well confirmed theoretically and experimentally, believe it or not)... what *kind* of questions do you think that people who have *not* mastered a field ask those who have, versus the kind of questions people who *have* mastered a field ask, and what kinds of answers can be given them? Think of how you have to talk to people who are tyros in some area in which you have a great deal of experience. Well, I think we can characterize the former questions, for the most part, as "trivial" relative to the latter. Of course there are always exceptions; I'm just giving a rough answer here, which I think is all that *can* be given. Here is a small fraction of related literature:
Gauthier, I., Skudlarski, P., Gore, J. C. and Anderson, A. W.: 2000, 'Expertise for cars and birds recruits brain areas involved in face recognition.' Nature Neuroscience 3, 191-197.
Gauthier, I., Tarr, M. J., Anderson, A. W., Skudlarski, P. and Gore, J. C.: 1999, 'Activation of the middle fusiform eface area increases with expertise in recognizing novel objects.' Nature Neuroscience 2, 568-573.
Kozbelt, A.: 2001, 'Artists as experts in visual cognition.' Visual Cognition 8, 705-723.
Maxwell, J. P., Masters, R. S. W. and Eves, F. F.: 2003, 'The role of working memory in motor learning and performance.' Consciousness and Cognition 12, 376-402.
Rossano, M. J.: 2003, 'Expertise and the evolution of consciousness.' Cognition 89, 207-236.
I think that characterizing the results of a study, or "talking about" something as "nontrivial" or a "nontrivial aspect" of something else, brings the same kinds of considerations into play. One is making a judgment as an expert, or judging what other experts will consider important about something.
Steven Ravett Brown
(48) Jean-Pierre asked:
In Plato's Apology, as part of Socrates defence he gives an account where he took an order from a [Spartan] Oligarch to kill a person. Instead of following the order he fled, knowing if caught he would be executed for disobeying the order. He used this account as an example of his virtue and his refusal to commit an unjust act. This example proves that Socrates held his own views on what is just and what is unjust in higher esteem than the law of the land. However In Plato's Crito, the dialogue that took place between trail and execution (which was only a 4 week period between his 'Apology speech and this one), Socrates refuses to escape or receive aid from his friends to escape on the basis that in doing so, he would be breaking the law, thus committing an unjust act. Surely this is a contradiction? In the trial he publicly announces he broke the law because murder was unjust, yet he doesn't use the same logic to escape being murdered himself? Was there another logic behind the decision not to escape? to be a Martyr? Or did he respect Athens's democracy over the Spartan Oligarch? If this is the case, then why did he accept the order in the first place? why was he collaborating, and only disobeyed when an order came along he didn't like?
You are right. Socrates does not confuse morality with law, neither Spartan nor Athenian Law. There is indeed another logic behind his decision not to escape. Socrates thinks (and publicly commits himself in the Apology to the view) that:
"to fear death is no other than to think oneself wise when one is not, to think one knows what one does not know. No one knows whether death may not be the greatest of all blessings for a man, yet men fear it as if they knew that it is the greatest of evils."
According to his conception of the philosopher as the man who knows that he does not know and abandons all pretence, no true philosopher would fear death. To act as if death where either good or bad would be to pretend to an essentially unavailable knowledge. Thus, for Socrates to act in the knowledge that (1) if he remains he will be killed, and (2) this would be a bad thing, would be for Socrates to give up being Socrates. Thus Socrates running away is just impossible, given who Socrates is.
One way (not the way I'd recommend, but a popular reductive tactic for lesser minds) to understand this is to say that for Socrates in the trial his whole life project is on the line. To run away from a death sentence of the court would be as good as dying, in the sense of: ceasing to be Socrates the Philosopher and becoming some pointless hypocrite in disgrace. Thus according to this reading Socrates stays not because he does not fear death but because he fears disgrace or hypocrisy more than death. Everything about Socrates' relation to the illusory goods of Honour and Public acclaim in the dialogues of Plato and the other reports tells me that this self-regarding reading of Socrates' behaviour at this point is the wrong one to have still, people flock to it when they are unable to swallow the point about death not being something a wise person can intelligibly fear even to the slightest degree.
There are also the references to the Homeric heroes in the Apology: there is a sense in which these people 'do not fear death'. But the analogy with Socrates is not precise and might be unhelpful, because there remains a sense in which the Homeric heroes *do* fear death, and in which their actions show the struggle of competing fears. The Homeric heroes fear dishonour, and might be said to be motivated by some public estimation of the good, rather than by their own autonomous philosophical lights. Their situation is like this: they do fear death, but they fear something else more, and so something interesting and *dramatic* happens in their psyche where they overcome the fear of death with another impulse they *struggle*, like a boat in high seas caught between wind and tide. In this the Homeric hero bears a comparison with suicide bombers which Socrates will not. Socrates is calm. His fearlessness is not like the wind overcoming the tide. When Socrates does not fear death, his lack of fear is not a question of not fearing death *compared to* the prospect of something else, but a question of not finding *any* fear of death intelligible, period. The Homeric Hero, like the suicide bomber/christian soldier, pretends to knowledge of death. The former thinks of death as a terrible eternal underworld, the latter imagines a heaven both pretend to knowledge and act in the light of that pretended knowledge. Indeed the suicide bomber/christian soldier inwardly pretends to both contradictory bits of knowledge at once, or else he would not be involved in inner struggles requiring moral or spiritual training as part of his outer struggle. But in any case both these types claim to know what being dead is like and act in the light of this pretended knowledge. This they call 'not fearing death'. The situation with Socrates is entirely different. He does ***not*** think that any knowledge of what being dead is like is available and for *this* reason finds fearing death an unintelligible and objectionable activity.
We (with our various confused and sub-conscious pretences to knowledge of the state being dead) may think of Socrates attitude here as either reprehensible stupidity or commendable bravery. He would reject both characterizations.
(50) Luciano asked:
Do colours actually exist or do humans conceptualize colour in our brains?
and Christian asked:
Are colours universal? If you and I were to look at the exact same picture, would you see the same colours that I see? You may say yes, because we both see the same "colour". Or do we? Are we just taught to claim to see the same things when our brains really perceive them differently?
The scientific explanation of colour is based on the makeup of white light (daylight), and its manipulation and interpretation by the human neuro brain structure. To put it very simply, white light impinges on the retina of the eye which is made up of a range of cells, including those described as rods and cones. Rods are concerned with the intensity of light, the cones, however, are concerned with colour. Objects are only seen by reflection, an object that does not reflect light cannot be seen.
Light is made up of different wavelengths, on striking an object, say a leaf on a tree, all the wavelengths are absorbed except one, this reflects and strikes the retina. The appropriate cones for receiving this particular wavelength are stimulated to pass an 'electrical' impulse along the optic nerve, to be received eventually in the visual cortex at the rear of the brain, where, in this case, the object is recognised as green. Reflection from a brick of a certain wavelength, the others being absorbed, will stimulate different cones which produce the colour red in the cortex. A mixture of reflected waves gives us the intermediate colours that we see in , say, mushroom or terracotta paint that some people like to paint on their walls. Thus it is alleged that colour is produced in the brain, to be observed by the 'mind'!? Which means that there is no colour in the world, just as there is no sound, taste, touch or smell. Science and some philosophy alleges that our entire world is somehow governed by the mind.
The philosophical problem arises from the fact that we have no access to another person's mind, hence there is no proof that two persons are seeing the same colour, we assume from the scientific theory that this is the case. There is nothing to prove that the parent who first taught us the names of colours was actually 'seeing' the same colour as ourselves. So it boils down to a question of names, a parent points to something he/she has always known as blue, utters the name, the child, whatever colour he/she sees repeats "blue". Hence, so long as we all use the same name , whatever colour we actually perceive is of no consequence in identification of colours. It is another of Wittgenstein's language games. However, one would venture to say that in the order of things it is highly likely that we all see the same colours, it is just that we cannot 'prove' what goes on in another person's mind, each individual is an island, depending on language and gesture to communicate thoughts. The same goes for seeing shapes or perceiving situations.
(51) Darren asked:
I contend that reason can only confirm the reality of the Self, since everything else is experienced within and by that Self. Existence is what we are and what we experience within. Why do philosophers spend so much time pondering realities beyond themselves when nobody can know anything beyond itself? Isn't a belief in material reality a philosophical crime in the sense that philosophy should be devoid of leaps-of-faith?
In the history of Philosophy, there are two quite distinct traditions about the nature of the relationship between "the Self" and what we think we perceive what we think is real. They are the Idealist, or the "Inside-Out" tradition and the Realist or "Outside-In" tradition. (I like the more descriptive labels. I feel they are less confusing, since the Idealist/Realist dichotomy is used in many different ways and many different places within philosophy.)
The Inside-Out (Idealist) Tradition The "Inside-Out" tradition is best exemplified by the famous quote from Rene Descartes "Cogito, ergo sum!" "I think, therefore I am!" Philosophers of this tradition start with the incontestable premise that "I think", and deduce from that the inescapable conclusion that consciousness is the fundamental given of metaphysics. Their argument is that to deny the premise "I think", or that "I am conscious" is a logical contradiction. The very fact that one is denying it necessitates that one is thinking and is conscious thus invalidating the proposition.
However appealing this approach is, it suffers from one fatal flaw that no philosopher has ever managed to bridge. In your question, you have highlighted this problem. Philosophers of the Inside-Out tradition maintain that our modes of consciousness and cognition modify or process the sensory inputs, so that what our consciousness is aware of as sensory evidence must be regarded as the products of our consciousness rather than unbiased evidence of reality. In that event, goes the inescapable logical conclusion, either we can know nothing about the nature of an alleged external reality (as you suggest in your question), or anything that we can know about such an alleged external reality must be provided through other means than our senses.
There is no logical line of reasoning that can proceed from the basic premise that consciousness is the fundamental given of metaphysics, to the conclusion that there is a reality outside of one's own consciousness. Since there is no way to validate the evidence of the senses, there is no basis from which to conclude that the sensory evidence is valid. Philosophers of the Inside-Out tradition are therefore forced to conclude that all that is perceived, as well as all the contents of consciousness is actively created by the nature of consciousness the "Self" in your parlance. As it is impossible, therefore, to logically derive the existence of an external reality, there can be no logical foundation for any constraints on the nature of the contents of a particular person's consciousness.
So we have philosophers like Berkeley who argue that there is no external reality. What we think of as "reality" is but ideas in some consciousness specifically God's consciousness. And we have Kant who argues that our understanding of the noumenal world (the un-perceivable and unknowable reality that is the foundation beneath our sensory perceptions) is governed by the structure of our consciousness.
The proponents of the "Inside-Out" line of reasoning support their arguments with examples and analyses based on evidence from the senses. Which is, of course, a logical contradiction since they argue that the evidence from the senses cannot be trusted. They assume that consciousness, as prior and primary to the sensory evidence, must generate our understanding from the evidence of our senses. Since this understanding is not a pure product of our senses, therefore what we understand about our sensory perceptions cannot be trusted as evidence of an objective reality.
Therefore, there can be no logical necessity for any standardization or similarity of the contents of consciousness from one person to another. In fact, there can be no logical necessity that there exists anything other than one's own consciousness. Any suggestion that there exists a reality, or that there exists other minds, is founded on untrustworthy evidence from the senses. The pure version of Idealism inescapably drives the logic towards Solipsism. And the only escape is to posit some unsupported additional premise (like Berkeley's addition of God) that can provide a loop hole.
Because it denies the existence of any form of objective reality, the Inside-Out tradition logically results in "Subjectivist" notions of Truth, Knowledge, and Ethics. The philosophy of Kant is perhaps the pinnacle of this school of thought.
There is also a sub-tradition maintained by those philosophers who start with the same "Inside-Out" premise, but despair over the subjective consequences and proclaim the "Nihilist" school Truth, Knowledge and Ethics are impossible, illogical, and invalid pursuits for inquiry. The once popular school of "Logical Positivists" are more or less of this school. Which is probably a good explanation why Philosophy and Philosophers as topics of popular awareness are in such ill repute.
The Outside-In (Realist) Tradition The Outside-In tradition is best exemplified by Aristotle. Philosophers of this tradition start with the premise that thinking and consciousness are processes not things. By the very nature of what a process is, in order for a process to "exist" (be in the process of processing) there must be something that is being processed. To think is self-evidently to think about something. To be conscious is to be conscious of something.
Philosophers of this tradition start with this premise and acknowledge that by the nature of processes there must first be something about which I can think or of which I can be conscious, and deduce the inescapable conclusion that the existence of something is the fundamental given of metaphysics. The argument is that to deny the existence of something is a logical contradiction. The very fact that one is denying that something exists necessitates that one is thinking about and is conscious of something thus invalidating the proposition. (By the act of thinking, one demonstrates that the thing that is thinking, and the thing that it is thinking about, both exist.) This argument is most succinctly (if not most cogently) expressed in the basic axiom of Randian Objectivism "Existence exists".
Start with the premise of a reality that exists (i.e. is "real") as the fundamental given of metaphysics. Add to that the realization that if thinking and consciousness are processes that are about and of reality, then reality must exist prior to and independent of those processes. You can't have a process in operation, without something being processed. You can't be conscious, without being conscious of something. But a process is not necessary for the existence of something. Thus the premise of a reality that exists as the object of the process of thinking and consciousness, necessitates that reality is objective and independent of those processes.
If reality is not "real" (ie. objectively existent), then the information provided by our senses is not a valid basis upon which to base conclusions about the nature of Reality. For Reality to be other than "real", would mean it would have to be "un-real" (non-objective and/or non-existent). And "unreal" means just that something is imaginary, or ideal, or constituted by our consciousness.
The approach that is more in keeping with "Common Sense" is the view that "out there" is not "in here". That there is a reality that is outside oneself, that does not respond to the whims and notions of one's conscious attention, and that does not disappear when one's consciousness is focused elsewhere. If reality is "real", then the information provided by our senses is a valid basis upon which to base conclusions about the nature of Reality.
There are numerous writers of the Outside-In (Realist) school of philosophy, beginning with Aristotle, who have written excellent expositions on the 'real' and 'objective' nature of Reality. Among the more recent of these are Ayn Rand(1), David Kelley(2), and William P. Alston(3). I can do no better than refer you to the works of one of these authors. They have done a much better job than I could possibly do, and at far greater length than this text would permit.
Perception and The Outside-In (Realist) Tradition The "problem of perception" arises when one views perception as a three step process:- (i) the reception of environmental stimuli at the sensory organs; (ii) followed by some extra-mind neural processing; (iii) and finishing with some form of presentation to the mind for evaluation and consideration. The three step process almost demands the thinker invest all sorts of possibilities for deception and confusion into that middle ground between the retinal image of the chair and the mind's perception of the chair. From a basis in this model, what one "sees" at step (iii) can be, and apparently often is, different from the sensory impression at stage (i). With this view as the paradigm, one cannot avoid talking about things "as they really are" as different from things "as they appear". And from there, one is drawn almost inevitably into the sceptical paradox of denying the possibility of knowing anything about "things as they really are" (if indeed such a thing exists) whilst driving the car to work during rush hour.
The problematic three-stage model is a tempting error to anyone from the Inside-Out (Idealist) Tradition, or anyone with a penchant for viewing the mind as more than just neural processes within the brain (a Dualist). To anyone with an overt or covert commitment to Idealism or Dualism, anything other than a three-stage model seems to be obviously wrong. As the question points out, to an Idealist who must deny the existence of an external reality, reason can only confirm the reality of the Self, since everything else is experienced within and by that Self. Existence is what we are and what we experience within. For a Dualist, who must deny the identity of the Self and the Brain, neurological science has followed the nerves "back" from the sensory organs, and demonstrated that all there is, no matter how far "back" you look, is merely electrical signals between different sets of neurons. So obviously, there must be some sort of "theatre" where all these electrical signals get translated into some form of "image" that the mind can then understand and be aware of. Obviously, the mind is not aware of the electrical signals that are being exchanged during all that second-stage processing.
With the three-step, Idealist or Dualist, model of perception, one can entertain all sorts of fancy thought experiments ranging from the Brain in a Vat to Descartes' Demon, where the mischief is located somewhere between the sensory receptors that receive the image of "things as they really are" and the mind that receives the image of "things as they appear". One can then argue that what the mind "perceives" is not what the senses receive from the environment. And therefore, even in the absence of mischief, what the mind perceives as the way the world "appears" is not necessarily the way the world "really is". And since we can never know whether some perception has been the result of mischief along the way, we can never know "things as they really are". Of even if there is such a thing as "the way they really are".
Which raises the question of just what exactly would be the nature of some thing "as it really is" as opposed to the way that the thing "appears" if in fact there is such a thing at all. The best answer that the Dualist can provide is Kant's. The phenomenal world (the world "as it appears") is in some way regularly dependent on the noumenal world (the world "as it really is"). But that does not really address the question of just what it would mean for something to be "as it really is" as opposed to how it "appears". The obvious intent of distinguishing between the two, is to permit that "things as they really are" can be different from "things as they appear". But since we can never determine what that difference is, and can only ever determine how things "appear", it leaves unanswered the question of just how things could be "as they really are" if that is different from how they "appear". And of course, it leave unanswered the question of whether there is such a thing as "how things really are". It leaves unaddressed the possibility that there is nothing at all outside of "things as they appear". Which, as I mentioned above, inevitably leads to Solipsism. But if they are in fact different, is it possible to conceive how they might be different? Indeed, if they are in fact different, is it possible to conceive of any answer to the question asked? It is even possible to conceive of "things as they really are" in a way that is different from "things as they appear"?
The significance of this question is highlighted when one considers just how one navigates a car through rush hour traffic on the way to work. The tolerances that apply to rush hour driving are pretty narrow (especially on a rapidly moving highway). It would not take much of a difference between the way things appear and the way things really are to cause an accident. Yet there are very few accidents that are attributed to such a difference. Which seems to imply that there is no practical, operational, day-to-day difference between "things as they appear" and "things as they really are". So why do philosophers make such a great to-do about such a difference if it doesn't seem to exist on a practical level? The unanswerable nature of this question (given the three-stage model of perception), is an indication that the concept of a difference between "things as they really are" and "things as they appear" is not a clear one. And that gives a clue to how to resolve the paradox.
The solution to this paradox is to avoid taking the first step. Reject the Inside-Out (Idealist) Tradition in favour of the Outside-In (Realist) Tradition. And then change the initial paradigm from a three step process to a two step process:- (i) the reception of environmental stimuli at the sensory organs; (ii) which is itself the presentation to the brain/mind for evaluation and consideration. With a two-step model as the basis, there is no longer any room for a separation between "things as they really are" and "things as they appear". The presentation that the brain/mind receives is the image of "things as they really are". That gives complete meaning to both phrases, explains the regular dependence between the phenomenal and noumenal worlds, and answers that unanswerable question. There are no traffic accidents attributable to the difference between "things as they appear" and "things as they really are" because there is no difference. "Things as they appear" is "things as they really are".
To a Realist-Monist such as myself, electrical signals between different sets of neurons is what the mind is. The "theatre" where sensory data gets translated into some form of image that the mind can understand is just exactly the initial sensory receptors the place where environmental stimuli first get translated into electrical signals. The impact of certain wavelengths of light on the retina *is* a sensation of red. The impact of a certain frequency of vibrations on the cochlear nerve *is* the sound of Middle C. The retinal image of the chair *is* an image of the chair as it really is. And the mind perceives that image from the retina. The chair "appears" to the mind/brain "as it really is". The problem of rush hour driving is just one familiar example of the evolutionary pressures that would ensure a seamless union of "things as they are" with "things as they appear". Any differences between the two would have had a tendency to get our ancestors killed. Since it is indisputable that we are here, our ancestors were obviously able to avoid that source of error. Hence the unavoidable conclusion that evolutionary pressures would ensure that there is no such difference.
Evolutionary pressures also, by the way, explain the point often raised by critics, that we are designed to perceive objects that are in some sense like ourselves. At each stage in our evolution from simple replicating chemical molecules to complex multi-celled and conscious organisms, the economics of dealing with evolutionary pressures would ensure that we would perceive only those environmental threats that we could deal with. An individual Escherichia coli bacterium would have little use for an ability to perceive the tiger hiding behind a bush and his intended lunch. But would have every use for an ability to detect food, and react to a deleterious chemical environment by wriggling away. In a similar way, the most significant environmental features for human beings food and physical threats are almost all on roughly the same physical scale. It has only been quite recently (say the last 200 years) that the threat of micro-life has been greater than the threat of a tiger behind the bush or simple starvation.
(1) Rand, Ayn; Introduction to Objectivist Epistemology, Expanded Second Edition, Edited by Harry Binswanger and Leonard Peikoff; Penguin Books, USA, Inc. 1990; ISBN-0-453-00724-4
(2) Kelley, David, The Evidence of the Senses, A Realist Theory of Perception; David Kelley; Louisiana State University Press, 1986; ISBN 0-8071-1476-6
(3) See for example Alston, William P.; Realism and Anti-Realism; A Sensible Metaphysical Realism; The Reliability of Sense Perception;