I’ve created a new thread based on the discussion below as it outgrew the ‘Favourite Philosophical Ideas’ thread in which it originated.
The Bent Stick
The ‘bent stick’ objection is easily dealt with. The objection was raised against Berkeley’s esse est percipe, (‘to be is to be perceived’) and discussed in the third of his Three Dialogues betwee Hylas and Philonious (Jonathan Bennett translation from Early Modern Texts in which Hylas represents the sceptic.)
Hylas: Since, according to you, men judge the reality of things by their senses, how can a man be mistaken in thinking that the moon is a plain shining surface, about a foot in diameter; or that a square tower seen at a distance is round; or that an oar with one end in the water is crooked?
Philonous: He is mistaken not with regard to the ideas he actually perceives, but in what he infers from his present perceptions. Thus in the case of the oar, what he immediately perceives by sight is certainly crooked; and to that extent he is right. But if he infers from this that when he takes the oar out of the water he will see the same crookedness, or that it will affect his sense of touch as crooked things usually do, in that he is mistaken. Likewise, if from what he perceives in one place he infers that if he moves closer to the moon or tower he will still experience similar ideas, he is mistaken. But his mistake lies not in what he perceives immediately and at present (for it is a manifest contradiction to suppose he could err about that), but in the wrong judgment he makes concerning •the ideas he thinks to be connected with the ones he immediately perceives; or concerning •the ideas that—judging by what he perceives at present—he thinks would be perceived in other circumstances. The case is the same with regard to the Copernican system. We don’t perceive any motion of the earth while we are standing on it; but it would be wrong to infer from this that if we were placed at as great a distance from earth as we are now from the other planets we would not then perceive the earth’s motion.
Kant’s Criticism of Empiricism
Berkeley was one of the British empiricists, saying ‘all knowledge comes through sense-perception’. He didn’t doubt the reality of objects, but disputed that sensory impressions were caused by ‘material substance’. Hence his ‘esse est percipe’ meaning ‘to be is to be perceived’. Berkeley is generally interpreted as a subjective idealist.
Immanuel Kant took pains to differentiate himself from Berkeley, especially after critics tried to equate Kant’s approach with Berkeley’s after the First Edition of the Critique of Pure Reason was published.
Kant’s criticism of empiricism (which is the usual basis of realism) is that it overlooks the role the mind plays in the interpretation of experience. Realism presumes the world is just so, perceived or unperceived, and that its existence is unproblematic. It is up to scientific method to determine its ultimate nature which is gradually elaborated and refined through further progress.
But Kant showed that the mind is not tabula rasa, a blank slate upon which experience leaves impressions. It is an active agent, that construes and interprets what it sees in terms of the innate categories of experience (ref).
I claim that despite the centuries that have elapsed, Kant’s ‘Copernican Revolution in Philosophy’ (‘things conform to thoughts, not thoughts to things’) remains a defensible position.
The problem here is to say that ‘ideas represent things.’ Because then you have to compare the idea with the thing! And how can we occupy a perspective where we have the thing on the one hand, and the idea, on the other?
Kant also anticipates this:
Truth, it is said, consists in the agreement of cognition with its object. In consequence of this mere nominal definition, my cognition, to count as true, is supposed to agree with its object. Now I can compare the object with my cognition, however, only by cognizing it. Hence my cognition is supposed to confirm itself, which is far short of being sufficient for truth. For since the object is outside me, the cognition in me, all I can ever pass judgement on is whether my cognition of the object agrees with my cognition of the object.— Kant, 1801. The Jasche Logic, in Lectures on Logic
This is the pitfall of the style of representative realism, a criticism which has often been levelled at empiricist philosophers, John Locke in particular.
So, in conclusion, I maintain that the shortcoming of realism, whether naïve or scientific, is that it fails to apprecate the foundational role of the mind in the interpretation of experience. We don’t natively ‘see things as they truly are’. That is what science aspires to do, and which it can do very well — but in specific contexts, in which the objects of analysis and the conditions of observation are carefully considered and specified. But our lived existence is not like that. The world we live in is also constituted in large part by the way in which we understand it and the meaning we impute to it. That is what realist philosophies tend to overlook.