On our now not so recent episode about Berkeley, with David Hilbert, I said in passing that idealism, in some form or other, is permanently tempting. Don't get me wrong, I don't believe in idealism. I consider myself a realist and a physicalist. Not only do I think that the world is (largely) independent of mind. I also think that the mind is ultimately just a part of that mind-independent world. That is, the mind is ultimately built out of and reducible to stuff that is not yet mind. Or so I would argue. So I don't come here todefendidealism. Neither do I come to refute it -- not exactly anyway. Lots of philosophers have claimed to have decisively refuted one form of idealism or another, but I suspect that such decisive refutation is probably not to be had. Although I don't for a second endorse idealism, I think it is worth ruminating on its (dark) allure just for a bit.

Idealism is a mansion containing many different rooms, some more elegantly furnished than others. Berkeleyan idealism, the ur-form of idealism, is a pretty spare thing compared to Kant's "Transcendental Idealism" which we will no doubt explore a bit to day on the show. Though the latter has sometimes been said to be just a fancied up form of Berkeleyan idealism, that construal does inadequate justice to the richness and complexities of Kant's philosophy. Kant's understanding of the constructive and combinatorial powers of the human mind vastly exceeds anything on offer in Berkeley's philosophy. Indeed, despite the fact that I reject his transcendental idealism, I tend to think of Kant as an early and great cognitive scientist. He was really an amazing student of the human mind, much more astute than John's favorite philosopherDavid Hume-- though Hume, too, had many deep and lasting insights into the mind.

After Kant, Idealism, especially in Germany, takes on many and variegated forms. Though our show onShchopenhauertouches on one form of post-Kantian idealism, I can claim no expertise in this rich period in the history of philosophy. I do currently chair a department that has perhaps the single best collection of scholars of German Idealism in the English speaking world. Whether that's blessing or a curse, I'll leave to others to judge. This preface is just a way of warning you that I myself am content to paint with a very broad brush here. If you really want to know about the many rooms in that philosophical mansion called Idealism, I'm not really the right philosopher to serve as your guide.

Idealists of all varieties seem to share a certain deep puzzlement over how "transcendental realism" could even possibly be true. By transcendental realism I mean, roughly, the view that our "ideas" somehow represent, give us cognitive and perceptual access to, and thereby enable us to think about and perceive a world not of the mind's own constituting and not in any sense contained within the mind.

为什么有人会觉得我们感知和思考的世界不包含在头脑中，也不完全由头脑构成，这一观点令人费解呢?相信我们的思想和感知能让我们接触到某种“外面”的东西，这难道不是最自然的事情吗?

显然不是。从历史上看，这种困惑可能始于“idea”这个概念。这个想法有几个不同的组成部分使得理想主义成为一个诱人的选择。首先，人们认为想法是某种内在的心理现象。第二种观点认为，概念代表了它们所代表的“相似性”。人们很快就会注意到，一个想法与另一个想法的相似程度要高于它与任何非想法的相似程度。离得出结论只有很短的一步，即我们的想法永远不会“像”任何心灵外部的现实，因此永远不能代表任何独立于心灵的现实。

This admittedly quick little argument doesn't begin to do justice to the subtlety of various actual arguments for idealism. But since not much of the remaining allure of idealism in the 21st century is depends on arguments directly tied to the idea-idea, I won't try to do better justice to the detailed arguments for idealism that start from the idea-idea. The idea-idea, especially, its resemblance theory of representation, fell out of repute long ago. Kant, for example, had already rejected it and replaced talk of ideas with talk of "concepts." Thoroughly modern representationalists have many views about how representations connect up to reality, but mostly they don't go in for simple resemblance theories thereof. Some take linguistic representations to be the paradigm of a representation, for example. The word 'snow' doesn't resemble snow in any interesting ways that I can think of but it "stands for" snow nonetheless.

那么，如果一个人拒绝了"理念-理念"及其"表征-表征关系"的相似性理论，那么什么会诱使他去唯心主义呢?一个可能的答案与我所谓的“表征优先于被表征物”的信念有关。如果你像许多哲学家一样认为，我们所有的思想或知觉都涉及某种内在表征的部署，你可能会认为不可能“走出”表征。我们总是与自己的表象打交道，而不是与一个赤裸裸的对象打交道。如果事物总是以思想或知觉的形式呈现在我们面前，那么它们只是通过我们的表象本身呈现出来的。(顺便说一句，类似这样的洞见是康德自身先验唯心主义的核心。)

This way of thinking doesn't yet give rise to any particular form of idealism, to be sure. Many representationalists are also realists. But if we ask just what an object is, a certain way of looking at objecthood leads pretty naturally to some form or other of idealism. You could think -- though I don't think you should -- that an object is justwhateveris "represented" by certain sorts of representations, representations that play a certain role in an overall system of representations. Never mind exactly for now just which sorts of representations and which roles. But if you think the role playing representations somehow precede and determine the objects, rather than following and being determined by them, you've taken a first step toward idealism.

Idealists tend to think that the very concept of an object is nothing but the concept of a something that is tied to our representations in a certain way. And they tend to think that this is some sort of a priori truth about our representations. If you start thinking this way, you could quickly get yourself into believing that "objects" are just a sort projection from or construction out of our representations and relations among them.

Why should anyone believe in the priority of the representation over the object? Idealism starts with a kind of "how else could it be" impulse. Think about it this way. We realists tend to think that our representations sometimes manage to "match" a world that is entirely independent of us. But this "external" world is supposed to make itself manisfest to our minds, realists admit, only through its relentless rush upon the portals of sensation. But this inward rush, the realist will also have to admit, is really just bare energy that does nothing but energize our nerve endings. It's not as though through the inward rush upon sensation the external world somehow directly "imposes" truth tracking representations upon us. As Berkeley puts it somewhere the "external" world does nothing to the eye except to shake the optic nerves. Yet, somehow the energized shaking of our nerve endings gives rise to a vast and varied plethora of representations -- representations of time, space, cause, effect, persistence, change, and on and on. How does the mere energized shaking of our nerve endings manage that?

One only need read, say, Hume, to convince oneself that these representations can't quite be "derived" or "deduced" or even "induced" from the bare inward rush of energy upon the portals of sensation. They go beyond -- way beyond -- anything merely "given" in sensation. If you accept that Humean conclusion you might be tempted to conclude that a our representations as of an "external world" of objects arrayed in space, rushing in upon the portals of sensation, is some sort of illusion and that many of our representations are groundless and deserve to be abandoned. In some moods, Hume seems to flirt with such the view that many of our representations as of an external reality are groundless. But his finals views are actually quite subtle.

An alternative path from Hume's insights -- which are genuine insights -- is represented by Kant. (Kant claims, by the way, that reading Hume awoke him from his "dogmatic slumber.") Hume is right, according to Kant. We don't derive our representations of cause, effect, persistence, change, space or time from the inward rush of sensation. Rather, we impose them upon the inward rush and thereby "constitute" or "create" the world -- at least the world that we experience -- which is the only world that we can know. The representations of space, time, cause, effect, persistence are already resident in the mind, prior to the inward rush. They are deployed by the mind to "organize" the inward rush. In organizing the inward rush via these pre-given representations, we structure and order the world. The structure and order that we impose on the inward rush is not there before we do our thing. It's not something we find in the inward rush.

Why is this a tempting idea? In large measure its allure results from the its promise to explain, in a way that few competing theories do, just how we mamage to cognize a highly complex, structured and ordered world, on the basis of the meager deliverances of "brute" sensation.

It comes with a cost, though. If the order and structure we cognize in the world is merely the mind's own imposition, that means we can't really know anything about the world "in itself." Indeed, it's fair to wonder how an idealist, even a Kantian transcendental idealist, can believe in the existence of a mind-independent world at all.

Personally, I find that an inordinate cost. But this is not the place to talk about how we can avoid paying that cost.