Freedom of expression is a very great good and so justifies allowing considerable (though not unlimited) psychological pollution. There may not be such a potent compensating good in the case of physiological pollution. It may be that a policy of additional legal restriction on psychological pollution would carry a greater moral cost than does the current legal restrictions on physiological pollution.

Perception is not ingestion: when you see a tree, the tree does not enter your brain. Moreover, seeing does involve the creation of an image on the backs of your eyes. But it does not follow that you only ever see an image. Maybe an analogy to a photograph will help. A photograph of a tree is an image; but it is not a photograph of an image, it is a photograph of a tree. Similarly, seeing a tree may involve an image of the tree, but what we see is the tree, not the image.

The past can't change, but what happened in the past affects what will happen in the future. Suppose that you didn't water your plant yesterday. If you believe this, then you will water your plant today and it will be fine. But if you falsely believe that you did water your plant yesterday, then you won't water it today and it will die. So the truth about the past matters.

The main way we cause pain to aminals is through the way we raise them in factory farms, so even if plants could feel pain (though like Richard, I bet they don't), we might be able to grow and harvest them without causing them any more pain than, say, we cause a free-range chicken. But if forcing them to grow in those straight rows causes them severe and prolonged distress....

I'm not sure that the sentence 'I exist' would be meaningless rather than just false if there were no referent for 'I', but the worry about question begging remains. And you are in good company with the funky chicken. Thomas Hobbes, in his objections to Descartes, asks why 'I think therefore I am' is any better than 'I walk therefore I am' ('Ambulo ergo sum'). One reply Descartes can make to Hobbes is that although existence follows equally from walking and thinking, Descartes has a certainty about his own thought that he does not have about his own walking (since he doesn't even at this stage know he has legs). There does seem to be something particularly secure about the belief that one is thinking -- how could one be mistaken? Indeed the belief is self-verifying. To believe one is thinking makes it so, since belief is thought. Believing one is walking, or dancing, does not make it so, sincd believing is not dancing. Still, I think the worry about question begging remains. For...

The meaning of life comes from what you do in your life: your activities and achievements. These are real even though you die, and would be no more real if you lived forever (though admittedly you would have time for a lot more of them).

At the most general level, it is difficult to see how free will is even logically possible, whether determinism is true or not. For if determinism is true, then everything we do follows from the laws of nature plus the state of the universe before we were born; and if determinism is not true, then there is a random element to what happens. Neither of these possibilities seems to leave room for free will. That was the bad news. The good news is that the fact that our actions have external causes is entirely compatible with their also having internal causes, in the form of our beliefs and desires. My consumption of the banana split was caused in part by the presence of that item on the menu -- an external cause -- but also by a desire on my part. If I had not had that desire, or if my desire to lose weight had been stronger, I would not have eaten the banana split. So insofar as the existence of internal causes is enough for us to hold someone responsible (as we often suppose it to be), then...

In this context, an argument is a set of claims -- the premises -- presented as a reason to accept another claim -- the conclusion. If you are checking for flaws, it is useful to distinguish two fundamentally different ways an argument can go wrong. The first is that one or more or the premises is false or at least unwarranted. The second is that even if all the premises were true, they wouldn't provide a good reason to believe the conclusion. The argument 'Some philosophers are horses therefore some horses are philosophers' suffers from the first flaw (false premise); the argument 'Some people are not philosophers therefore some philosophers are not people' suffers from the second flaw (premise does not provide a good reason for conclusion). When you are checking an argument, consider both types of flaw. Are the premises true? Do they provide good reason for the conclusion? In tackling the second question, it is often a good idea to ask yourself whether, if the premises were all true,...

Some objects simply aquire a function in virtue of being used in a certain way, like the rock I use to prop open my office door. But traits of biological organisms do seem to have natural functions, like the white fur of the polar bear, whose function is camoflage. There is a spirited discussion among philosophers of biology over just how to analyse biological functions, but the selected effects account is perhaps the most popular. On this view, an effect of a biological trait is a function if the trait was selected for by natural selection because of that effect. Thus camoflage is a function of white fur because it is in virtue of that effect that polar bears came to have white fur. Notice that not all effects of biological traits qualify as functions on this account. The heart pumps blood, and that is presumably an effect that was selected for and so counts as a function. But the heart also produces that adorable lub-dub sound; that is just as much an effect of the heart, but presumably not the...

I don't know how much this will help, but there seem to be three things associated with the color green: the experience of green inside your head; the disposition of certain surfaces to produce that experience, something which is not inside your head though it is defined in terms of something inside your head; and the molecular structure of certain surfaces out there that help to cause experiences of green. Most philosophers agree that all three of these things exist, but they disagree about which of them should be identified with 'the color green'.