Empiricism

We agreed (I think) that rationalists are right to argue that we cannot achieve certainty about knowledge unless we can generalize from particular cases (experience, observations, experiments) and form general principles or laws of nature. I think we could also agree that in order to do that we need to use the kinds of intellectual tools that rationalists say we have a priori knowledge of: maths, inferential reasoning, etc. But do we agree that we have knowledge of such tools innately or by intuition? Probably not.

Empiricists certainly argue that we can have knowledge only as a result of experience, and that includes knowledge of maths and inferential reasoning. They trace the foundations of all knowledge and all ideas back to the firm foundations (as they see it) of sense experience - that is, the basic, raw perceptions that reach our senses from the outside world. Hume called them "impressions". More recent philosophers have referred to "sense data". Whatever we call them, the point is that we cannot have any knowledge of the world except via our senses.

John Locke argued (against Descartes) that we are not born with any innate ideas; we arrive with "tabula rasa" minds - clean, blank, empty. The knowledge and ideas we acquire all come as a result of sense experience. Hume agreed with this, although he also thought that as humans we are born with a certain nature, dispositions, for example, to associate one idea with another, or to form habits of expectation, so that when we see item A we tend to expect item B. This was how he explained our inductive reasoning, causal explanations and our knowledge of the external world. "Hume's Fork" is his argument that all ideas and meanings can be traced back to impressions (sense experience). Ideas are faint copies of impressions. The impressions (sights, smells, sounds, etc) have impressed themselves, printed themselves, on our minds, and our memory of them is what we call "ideas", but of course we can combine ideas of basic impressions to create more complicated concepts and imaginary objects (eg golden mountain). As for analytic truths - Hume was dismissive: they cannot give us genuine knowledge of the world because they only recycle ideas we already have, being merely true by definition. All genuine factual knowledge (synthetic truths) derives from impressions, sense experience.

One major difference between Lock and Hume is that Locke believed our beliefs about the world were rationally justified, whereas Hume was more sceptical and thought they were only justified in so far as our natures (imaginations, habits, emotions) allow us to interpret the world in particular ways. He didn't think we could know what the external world was really like because we only ever see impressions, not the objects that (we assume) caused the impressions. Locke and Descartes were both Indirect Realists, believing that we could rationally infer the existence of the objects that cause our perceptions of them. The ordinary "common-sense" view is that we just see objects as they are. This is known as "Direct Realism", and Hume thought both the Direct and Indirect versions of Realism were equally shaky. So he was a kind of sceptic or anti-realist. He had been persuaded by Bishop Berkeley's arguments against Realism but he didn't follow him all the way to Idealism ("to be is to be perceived" - ie only perceptions actually exist) - partly because Hume couldn't believe in Berkeley's God, who ensures existence is continuous by perceiving everything! So Locke, Berkeley and Hume are all empiricists, because they all believe that we acquire knowledge from sense experience (a posteriori) not before it (a priori), but they represent different kinds of empiricism.

Next we will look at some criticisms of empiricism.