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By tradition, the problem that dictates where our knowledge is derived divides from two philosophical circles; those who affirm that our knowledge of the world comes from our senses, such as David Hume, an empiricist, and those who proclaim that it is only through reason that one can find truths about the world, such as René Descartes, a rationalist.

However, without our senses are we nothing? If we cannot see, feel, taste, smell or hear, what is left? But without thought, we are unable to understand the world.

Simply, does one obtain knowledge through via empiricism or rationalism?

  • All actual knowledge you can derive from your senses is that you know that you can perceive. I would consider this a proof for your existence. – eWolf Apr 1 '12 at 21:40
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    Do you mean logically epistemologically, or as a matter of neuroscience and developmental biology? You end up with very different answers depending on which question you ask. – Rex Kerr Apr 2 '12 at 1:31
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    To add on to Rex Kerr's comment, I think this question is extremely broad as it is. Perhaps you could specify to a certain school of thought on behalf of which you want an answer to respond? – commando Apr 2 '12 at 20:28
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    I'm slightly concerned about this question, as it is very broad (requires a huge summation of literature) and there is no single definite answer. In fact, the question can be compressed into one word: epistemology. Every single author in all of philosophy will have a different answer for you; I'm qualified to post an answer from the view of several authors and none of them would necessarily be "the answer"... – stoicfury Apr 9 '12 at 19:25
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+100

Consider how we may theoretically obtain information:

  • Directly, through our senses.
  • Built into our design, EG: instinct, reflexes, hormonally/pheromonally triggered behaviors, etc.
  • By rational analysis, principally induction and deduction.
  • Encoded, transmitted through our senses and then decoded. Language and most everything we've "learned" would fit this category.

    We distinguish this from normal/direct sensory data by noting that our bodies do not naturally know how to decode this information; we have to be taught how to consume it.

  • For completeness, we can't disprove that divine revelation/inspiration is possible.

Given all that, it should be obvious that "empiricism versus rationalism" is a false dichotomy. We get knowledge both ways and more.

~~~
As for, "What extent, does our knowledge derive from our senses?" Whole books can and have been written on just aspects of this, the question is very broad.

Consider a typical scene in our moment-to-moment existence, we might learn the following "facts" (probably automatically and without consciously realizing/verbalizing them):
(a) The remote is there, while (b) the beer is there, but (c) the wife is standing there. (d) She's holding a garbage bag. (e) I feel tension in my jaw.

In that scene, we know quite a bit directly from our senses, but most of our sensory data is filtered into responses and/or concepts automatically, then the raw sense data is mostly discarded. The individual photons and pressure waves are vital, but do not matter in and of themselves.

Note that we all can (and do) trust our senses with our very lives. Sure they have limitations and can be tricked, but these limits are almost always outside of what is required for our day-to-day survival. We would have long ago been crocodile chow were it otherwise. The limits of our senses are now known; they are predictable, and consistent across individuals and species.

Now back to that scene. The individual photons, sound waves, etc. were sensed, but it was how we accurately interpreted them that mattered. All animals have innate knowledge built-in to help interpret their senses into the fundamental (to life) concepts of the need/opportunity to: fight, flee, feed, or f..., er, fornicate.

It's automatic, but it is knowledge, and it is objectively right most of the time (or our parents wouldn't have lived long enough to breed). This knowledge was designed into our bodies by evolution -- a kind of meta induction.

So, at a fundamental biological level, the most important knowledge we have is not sense-percepts, but concepts that Mother-Nature inducted for us after collectively processing lifetimes of sense-percepts.

Even the existence and design of our senses is a kind of built-in knowledge. One thing that biology and neuroscience is teaching us, is that there is not "mind" versus "body", and there is no "inner control room" to the mind. A mind cannot exist without a body, and the whole body affects the mind (and vice versa). "Thought" and "knowledge" occur across a spectrum as a process; the structure of our brains greatly affects what we "know".

Studies of siblings suggest that "Nature" is still a substantial part of who we are and that "nurture" can effect only so much.

So, as animals, much of our knowledge is built in. We learn things via our senses, but it is how we interpret our senses, via deduction (most of it automatic) that keeps us alive.

As humans, we transfer massive amounts of information to each other via training and language. Initially, this information would have been concepts inducted from sensory observations by our ancestors (Or prepackaged by God, if you wish).
But, then new deductions could be made from those concepts, initially devoid of sensory data (discoveries in astronomy and physics have been made this way). However, in Science, such deductions are worthless unless they are eventually supported by sensory data.

Summary:
Sensory perceptions are the bedrock upon which all of our (useful, verifiable) knowledge is built. But, the bulk of what we currently know and use was long ago inducted into concepts or into the very design of our bodies and minds. Today, concepts, innate and otherwise are the dominant factor in our knowledge and in our survival.

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I think that the question betrays a misunderstanding of rationalism; Descartes does not argue against the notion that "our knowledge of the world comes from our senses"-- he simply argues that some knowledge (regarding mathematics and logic, primarily) come through reason alone.

So, answers to the question "To what extent does our knowledge derive from the senses?" are generally going to range from "A very large extent" to "Completely."

Within this range, however, there are a very large number of different opinions-- a number which exceeds the number of epistemologists who have addressed the problem, as many of them have changed positions several times over the course of their work.

If this problem interests you, I suggest you find an introductory textbook on epistemology; it will lay out the territory nicely.

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This is a difficult question to answer because while empiricism has a pretty solid requirement - all knowledge of the external world must derive from our senses - rationalism is not synonymous with Descartes and has a number of different formulations.

Descartes' view is perhaps the strongest form of rationalism. His claim is that we can never be certain about empirical evidence, and therefore we can never know anything based on such evidence. This position is not really defended by contemporary philosophers (as far as I know), and even Descartes himself had to engage in some mental contortions to defend the idea that intuitions are somehow more reliable (indeed, certain) than perceptions. See also the Cartesian Circle.

A more relaxed version of rationalism simply requires that some knowledge of the world may be known a priori. This thesis is far more attractive due to the fact that it seems to be easy to discover examples that fall into this category and (at the same time) disprove empiricism. For instance, it is true that

(P) Nothing can be both green and red.

This is a statement about the external world, but it seems obvious purely by reflection rather than via some set of experiences we've had in the world. Additionally, this proposition is not the same as

(Q) No proposition can be both true and false.

because one would have to derive a contradiction from the definitions of 'green' and 'red', and no one (again, that I know of) has been able to do so. (Ignoring scientific explanations, that is, because P doesn't seem to be something we learned in the last couple hundred years.)

Having said all that, there are still philosophers who hold to empiricism (see impossible colors as one route to a resolution of the above concern), so the debate is not yet settled.

  • It seems to me that the truth value of the statement P very much depends on what is meant by "being" a color. I can think of an enormous set of everyday objects that contain both molecules that emit "red" light and molecules that emit "green" light. – yamad Apr 10 '12 at 6:55
  • @yamad: true enough. Try the example from the perspective of a few hundred years ago, when we knew next to nothing about the physical nature of color. Whatever sense of 'be' works for that time period is the one we should be using. – ladenedge Apr 10 '12 at 16:33
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Does the assumption that all "knowledge" must fall neatly into one or other of the two categories of rationalism and empiricism, actually hold up? Or are they the wrong tools? Aren't the right tools the full richness of everyday language? To quote Stanley Cavell:

the philosopher who asks of everything we say, "True or false?" or "Analytic or synthetic?" has a poor view of communication... in something like the way a man who asks the cook about every piece of food, "Was it cut or not?" has a poor view of preparing food. The cook with only one knife is in a much better condition than the philosopher... The cook can get on with the preparation of the meal even if he must improvise a method here and there, and makes more of a mess than he would with more appropriate implements. But the philosopher can scarcely begin to do his work; there is no job the philosopher has to get on with; nothing ulterior he must do with actions (e.g., explain or predict them), or with statements (e.g., verify them). What he wants to know is what they are... If the philosopher is trying to get clear about what preparing a meal is and asks the cook, "Do you cut the apple or not?", the cook may say, "Watch me!" and then core and peel it. "Watch me!" is what we should reply to the philosopher who asks of our normal, ordinary actions, "Voluntary or not?" and who asks of our ethical and aesthetic judgments, "True or false?" Few speakers of a language utilize the full range of perception which the language provides... but to neglect it deliberately is foolhardy. The consequence of such neglect is that our philosophic memory and perception become fixated upon a few accidents of intellectual history.

I think Cavell's criticism can be readily applied to this question.

How much of philosophy is wisdom, and how much of it is an aversion to ordinary categories - a sense that, like physics, human understanding can and must be broken down to atoms and its boundaries and mechanisms worked out for us not to be made fools - fools to religion, fools to superstition, fools to ignorance? We're driven to dissect, and by dissecting we kill it. Ever noticed how whenever you hear "philosophy of", the meaning of the noun that follows tends to disappear into obscurity?

Epistemology is a rumination on knowledge by one struggling to, but never genuinely succeeding in, overcoming a denial of knowledge.

The quote is from Stanly Cavell's essay "Must we mean what we say?"

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