The philosopher, Rene Descartes, has said that it is possible to doubt all things except the existence of oneself (cogito ergo sum); that it cannot be doubted, despite how hard one endeavors. However, I am often questioning if that proposition is "truly" "indubitable". I desire to know if there have ever been any well-known or ancient philosophers who had not "concurred" with Rene Descartes regarding the cogito ergo sum; or if there are modern philosophers with great reputation, prestige, or respect within the philosophical community, who believe that the cogito ergo sum is "not" indubitable? Otherwise stated, it is "possible" to "doubt" the existence of oneself.

There are plenty of philosophers who have not agreed with Descartes' line of thought here, though they are not "ancient" philosophers, as Descartes did not propound the "proof", if that is what it is, until 1637, in the Discourse on the Method and, in a slightly different form, in 1641 in the Meditations . You can find some interesting material in the "Objections" to the Meditations , for example the Fifth, by Gassendi, or the Fourth, by Arnauld. Hobbes too, in the Second Objection, makes of Descartes' argument a triviality. How (he asks) can I know that I am thinking? 'It can only be from our ability to conceive an act without its subject. We cannot conceive of jumping without a jumper . . .'. Through the centuries Descartes' dictum has come under even more fire from different directions, for example from A.J. Ayer in Chapter 2 of Language, Truth and Logic . Descartes was only entitled to say that 'There is a thought now,' not 'I think', i.e. 'There is an I and it thinks', because...

What are your main objections about the way philosophy is taught to undergraduates today and is it any different than the way it was taught during your time as an undergrad? Just how much say do professors in philosophy have over what they want to cover? I only took two philosophy courses in school, but I found that the topic material was overly broad and covered too many philosophers; even the professors seemed overwhelmed with the readings. I think it would be more worthwhile if perhaps the students decided at the beginning of courses specifically on no more than three philosophers/topics to cover intensely since specialization results in a greater degree of understanding instead of general unconcentrated knowledge.

There are I think no objections to the way philosophy is taught to undergraduates today in US and UK universities. Courses are on the whole very well taught, there is a an emphasis on clarity and often on originality, and students learn a great deal of respect for decent argument, as well as sound scholarship. Courses on the history of philosophy have never been better, and this is true of courses in other areas as well. I believe you when you say that your school philosophy courses was too broad and "even the professors seemed overwhelmed with the readings." I have noticed this kind of thing before. You are absolutely right that "specialization results in a greater degree of understanding", though there is a place for the well-taught survey course. If I were going to offer a course on three philosophers, I would want the three to have a strong link, so for example a course on "Descartes, Spinoza and Leibniz", "Stewart, Reid and Hamilton", or "Russell, Moore and Wittgenstein".

Just what is the difference between a lawyer and a legal philosopher? Does the legal philosopher care more for metaethics and less for social norms?

A lawyer is someone who practises law, or perhaps studies it, an attorney (in the US) or a barrister or solicitor (in the UK), someone who might have little or no interest in the philosophy of law, or in the the concept of law in the abstract. A legal philosopher, on the other hand, is a philosopher, often or typically today an academic person, one who studies and perhaps contributes to the philosophy of law. The philosophy of law is one of the subject areas within philosophy (such as the philosophy of science, the philosophy of religion, ethics, the theory of knowledge, metaphysics, and so on) in which one studies the question 'What is law?' - to be distinguished of course from the question 'What is the law ?' - which is not a philosophical question at all. Or a philosopher of the law might be interested in the question what it is that makes law "valid". There is little doubt what the laws were in say 1935 Germany, e.g. the Nuremberg laws prohibiting the marriage of citizens ("Staatsangehoerigen")...

Why do so many scholars and intellectuals think that language is necessary for thought?

My answer is a little different from Olilver's. Why do so many scholars and intellectuals think that language is necessary for thought? Answer: Because it really is easier to think about definite rather than indefinite things. But indefinite and formless things also have to be thought about. It takes more of an effort of course to think in a pathfinding sort of a way about something new, and one may or may not be thinking "in" language, whatever that means (muttering to oneself, sub-vocally?) If one is trying to come to an understanding of some hard and new logical or mathematical matter, it may be more like shaping forms in ones mind, and then moving them, and less like chattering in French. If one insists on calling "shaping forms", or whatever the metaphor is "a kind of language", then of course the claim is drained of any content, and with that of any interest. People of say that mathematics is a language, or a "language", something like a language. But it has a function and a status very different...

Is there a philosophical similarity between what one can't do because it's morally wrong, what one can't do because it is contrary to one's own aims, and what one can't do because the laws of physics prevent it? Does philosophy have something to say about these various uses of the same word that we find in several languages?

To me it seems that the use of the word "can't" and its meaning is the same in all three settings (moral, prudential and physical). "Can't" means there's a contradiction in saying that you do the thing you are said not to be able to do. But the contradiction does not appear without the addition of the "laws" or principles of ethics, or the statement of what one wants, or the laws of physics. There is one exception to this principle. "Can't" in logic and logic-derived fields asserts a contradiction without any body of auxiliary propositions. 'I can't lift 1000kg' means that given the facts of my strength and some facts of physics, there is a contradiction in saying that I lift 1000kg.

why is it that we see sunsets, mountains, life forms, geological formations, etc. and consider them to be beautiful.

A helpful answer might be that we see sunsets and mountains and so on as beautiful because they are beautiful. The reason I say that this answer is helpful is twofold. It moves the question away from the bias of a model in which (a) there is no beauty in nature, but (b) we project it onto nature, which together raise the question © 'Why these projections and not others?' That is all built into the question. The second helpful thing, as I see it, about the answer that I have suggested is that it puts the issue squarely on top of the traditional question what beauty is.

More of an observation than a question, about "compatibilism" in the free will "versus" determinism debate. In the short run, there is a strong correlation between life expectancy tables and the number of people who die in a calendar year. Somehow, even though on the level of the individual, many of these events may be due to "luck" (wow, that train just missed me; or wow, what a freak combination of factors to lead to such a bizarre accident); on the level of the population, the total number of deaths in a year can be "predicted" fairly well even if no individual death can be predicted. In the long run, life expectancy tables do change over time: collectively, each individual person uses what they learn about diet, exercise, cigarette smoking, etc. and makes adjustments in their day-to-day lives; and the aggregate results over time do reflect these changes. It seems to me that there is a good question buried here in this analogy but I can't quite figure out how to unearth it. Any thoughts from a...

You make an important observation for compatibilism. What your analysis does is to show that we can have predictability and law (in a regularity sense) with no implications for individual freedom. My decision to cross the railway track might lead to my death, and it might produce a number that fits the predicted number of deaths on railway lines in a year. Was my decision then not a free one? Hardly, because for that to be the case it has to be coerced or whatever the particular compatibilist line being taken is. The fact that there are h homicides a year in the United States, on average, and that without the homicide I commit the number would be h -1 has no relevance to the freedom or unfreedom of my act. Your point was of central importance to the classical compatibilists, who realized that knowledge and predication of what will happen have no tendency to undermine freedom. I know what I will do, but this could hardly be a reason to say what I will do is not free. It might even be a condition for...

I've read a few philosophers write that color theorists typically divide into two camps of those who say colors are scientific properties of objects and those who say that color only exists in the mind and are therefor subjective and illusory. These philosophers often offer some alternative to this dichotomy like the idea that colors should be thought of in more relational terms between subject and object. But can't colors be entirely mental or dependent on mental processes but not be illusory?

Clearly what is dependent on the existence of mental processes is not therefore illusory. Unlike many things, the existence of mental processes is dependent on the existence of mental processes. It does not follow that mental processes are illusory. But I think it should be said that there is little or nothing that philosophers have provided that could help us to understand what it means to say that a colour, the colour pink, for example, exists, or exists only, in the mind, or outside of it, for that matter. The mantis shrimp has at least eight colour receptors - it can also perceive circularly polarized light and its direction of rotation! - but the poor old thing does not have an awful lot in the way of a mind. Mind you, it can deliver a punch (with one hand!) at 10,000 g, enough to boil the water in front of it.

If I do something, is it fair to say that I am also _choosing_ not to do one of an infinite number of other things that I am not considering at the time of the choice? For example, if I ask somebody "What's your name?", is it accurate to say I am choosing not to ask them "Where are my walnuts?", even if the second question never even occurred to me?

No, it's a mistake to say that you are choosing not to do all those other things. When you decide to ask someone "What's your name?" it is not "accurate" or right to say that you have chosen not to ask that person "Where are my walnuts?" What is true is that you are not choosing to do the infinite number of things, and you are not choosing to ask where your walnuts are, but that is not at all the same thing as choosing not to ask where they are. Not choosing to ask my name is not a choosing, whereas choosing not to ask my name is. You can also see that it couldn't be right to say that you are choosing not to do infinitely many things - there just isn't time!