Empiricists

Locke, Berkeley, Hume, Mill

Empiricists believe that all knowledge comes from experience.

They generally believe that science is just a particularly organized way of learning from experience.

The 17th-Century empiricists (that is, immediately after Newton) were primarily sensationalists. That is, they believed that our experience consists entirely of sensations, that experience might be described in ways like this:

Looks like red patch to the left of green line.

It's hot.

Empiricism has at least two important serious problems

External world skepticism

It is hard, perhaps impossible, to get from sensations to knowledge of an external material world.

Many empiricists just gave up on an external material world in any ordinary sense of the term. They allowed themselves to be backed into endorsing

Phenomenalism

Roughly, phenomenalism is the view that there isn't anything behind the sensations, that not just our experience (sensationalism), but the world itself is nothing but patterned sensations.

Thus, Mill said that physical objects are just "permanent possibilities of sensation" (1865).

Inductive skepticism

The other problem is about the "permanence" I just mentioned: why should we expect that experience will continue to occur in the same patterns? Why should it be possible to learn from experience?

Hume even gave up on learning from experience—or, at least, that is a fairly standard interpretation of his work—but most empiricists felt that solving the problem of induction, that is, finding a way to defeat inductive skepticism, was an important part of defending empiricism.

In direct opposition to the empiricists, there were the rationalists.

Rationalists

Descartes and Leibniz believe that not all knowledge comes from experience. Some, for example, knowledge of one's own existence ("I think therefore I am") and mathematics comes from pure reasoning.

Kant's synthesis

Kant (1781) came along with a synthesis between rationalist and empiricist ideas that seemed, and still seems to some, very promising:

Our minds are structured in such a way that we inevitably reason about the sensations we receive along certain lines. What we learn about the world is largely a product of experience (empiricist strand), but it is experience structured by the inevitable (rationalist strand) structure of reason—without that structure, one could not learn from experience.

By building in the right structure, Kant could pretty nearly solve the problem of getting from sensations to an external material world. In some respects he could do even better: For example, he gave what he took to be proofs that space is flat and 3 dimensional, proofs that, while we no longer believe their conclusions, remain of interest today.

Idealism

Kant's external world is not prior to, a primary cause of, experience, but is instead constituted out of experience and reason. (It is hard to say anything uncontroversial about that aspect of Kant's work, but what I just said is certainly true under some interpretation of "constituted.")

Once you give up on a primary external world, it is natural to conclude that everything is made up of something that is in some sense mental, that is, _ideas, _ an umbrella term that may include both sensations and the products of reason.

Idealism was dominant in the 19th Century, and one strand of it culminates with Hegel (1807). Hegel is a controversial figure. Logical positivism, the view with which our main story begins, arose out of distaste for Hegelian idealism, and Hegel's works are often used—and even ridiculed—as examples of disastrous mistakes in doing philosophy to be avoided at all costs. Hegel is cast as the villain of the story. In the traditional anti-Hegelian account we inherit, Hegel took the development of the universe to be the development of the consciousness of the universe, and history (human history) exists in the service of developing that World Consciousness. That picture of the world came out of a reaction to Kant in something like the following way: if the world is a product of (sensation and human) reason, then the development of reason is itself the development of the world. Hegel took Kant's description of reason completely constrained by rational necessity, and replaced it with an historical picture of reason that improves and develops along certain inevitable lines, and that improvement and development is simultaneously the improvement and development of the world itself.

Russell and Moore, as young philosophers in England at the beginning of the 20th Century hated this World Consciousness stuff, in part for the ways in which it can be used to justify totalitarianism, and developed an anti-idealist philosophy firmly rooted in our ordinary experience and in science.

As the views of Russell and Moore led to logical positivism, Heidegger (1926) became prominent in Europe. Like Hegel, Heidegger's philosophy centers around the historical development of the way in which experience is conceived, and, like Hegel, Heidegger was used as an example of what one should avoid in doing philosophy. Heidegger was a Nazi and German nationalist; the logical positivists were internationalists (Neurath invented the modern system of international road signs) and, to varying degrees, socialists.

The Nazis drove the logical positivists (as well, of course, as many other philosophers, scientists, and mathematicians) to the United States, and that led to a flowering of philosophy here.

-- ShaughanLavine - 31 Aug 2005 - 27 Aug 2007