"Every one knows that the heavenly bodies move in certain paths in relation to each other with seeming consistency and regularity which we call [physical] law. ... No one attributes freewill or motive to the material world. Is the conduct of man or the other animals any more subject to whim or choice than the action of the planets? ... We know that man's every act is induced by motives that led or urged him here or there; that the sequence of cause and effect runs through the whole universe, and is nowhere more compelling than with man." Quoted in Lecture Notes on Free Will and Determinism by Norman Swartz.
“…one doubts existence of free will [because] every action determined by heredity, constitution, example of others or teaching of others.” “This view should teach one profound humility, one deserves no credit for anything…nor ought one to blame others.” From Darwin’s notebooks, quoted in Robert Wright, The Moral Animal, pp. 349-50.
“The inward persuasion that we are free to do, or not to do a thing, is but a mere illusion. If we trace the true principle of our actions, we shall find, that they are always necessary consequences of our volitions and desires, which are never in our power. You think yourself free, because you do what you will; but are you free to will, or not to will; to desire, or not to desire? Are not your volitions and desires necessarily excited by objects or qualities totally independent of you?” From Good Sense Without God.
"If the moon, in the act of completing its eternal way around the earth, were gifted with self-consciousness, it would feel thoroughly convinced that it was traveling its way of its own accord on the strength of a resolution taken once and for all. So would a Being, endowed with higher insight and more perfect intelligence, watching man and his doings, smile about man’s illusion that he was acting according to his own free will." From a piece written as a homage to the Indian mystical poet Rabindranath Tagore, quoted here.
And: “I do not believe in free will. Schopenhauer's words: 'Man can do what he wants, but he cannot will what he wills,' accompany me in all situations throughout my life and reconcile me with the actions of others, even if they are rather painful to me. This awareness of the lack of free will keeps me from taking myself and my fellow men too seriously as acting and deciding individuals, and from losing my temper.” From "My Credo" .
And: "I agree with your remark about loving your enemy as far as actions are concerned. But for me the cognitive basis is the trust in an unrestricted causality. 'I cannot hate him, because he must do what he does.' That means for me more Spinoza than the prophets." From a letter to Michele Besso quoted here.
And: "Human beings, in their thinking, feeling and acting are not free agents but are as causally bound as the stars in their motion." From his address to the Spinoza Society in 1932.
"I should . . . prefer swallowing one incomprehensibility rather than two. It requires one effort only to admit the single incomprehensibility of matter endowed with thought, and two to believe, first that of an existence called spirit, of which we have neither evidence nor idea, and then secondly how that spirit, which has neither extension nor solidity, can put material organs into motion." From a letter to John Adams on 3/14/1820.
“All theory is against free will; all experience is for it.”
“The human mind is impelled to action, or held in rest by some power, over which the mind itself has no control.” from Handbill Replying to Charges of Infidelity. “We often argued the question, I taking the opposite view.... I once contended that man was free and could act without a motive. [Lincoln] smiled at my philosophy, and answered that it was impossible, because the motive was born before the man.... He defied me to act without motive and unselfishly; and when I did the act and told him of it, he analyzed and sifted it to the last grain. After he had concluded, I could not avoid the admission that he had demonstrated the absolute selfishness of the entire act.” From Herndon, "Analysis of the Character of Abraham Lincoln," Abraham Lincoln Quarterly 1 (Dec. 1941): 411; Herndon and Weik, Abraham Lincoln, 2:148, 306, quoted in Abraham Lincoln and the Doctrine of Necessity by Allen C. Guezlo (a most interesting, well-referenced paper).
"The causa sui is the best self-contradiction that has been conceived so far; it is a sort of rape and perversion of logic. But the extravagant pride of man has managed to entangle itself profoundly and frightfully with just this nonsense. The desire for ‘freedom of the will’ in the superlative metaphysical sense, which still holds sway, unfortunately, in the minds of the half-educated; the desire to bear the entire and ultimate responsibility for one’s actions oneself, and to absolve God, the world, ancestors, chance, and society involves nothing less than to be precisely this causa sui and, with more than Baron Münchhausen’s audacity, to pull oneself up into existence by the hair, out of the swamps of nothingness." Quoted in “The Buck Stops – Where?”, an interview with philosopher Galen Strawson.
“When a man acts in ways that annoy us we wish to think him wicked, and we refuse to face the fact that his annoying behavior is the result of antecedent causes which, if you follow them long enough, will take you beyond the moment of his birth, and therefore to events for which he cannot be held responsible by any stretch of imagination… When a motorcar fails to start, we do not attribute its annoying behavior to sin, we do not say, you are a wicked motorcar, and you shall not have any more gasoline until you go.” (Richard Dawkins takes exactly this line at Edge.Org in his case against retribution.)
“You are free to do what you want, but you are not free to want what you want.”
“The mind is determined to this or that choice by a cause which is also determined by another cause, and this again by another, and so on ad infinitum. This doctrine teaches us to hate no one, to despise no one, to mock no one, to be angry with no one, and to envy no one.”
“Where are there are two desires in a man's heart he has no choice between the two but must obey the strongest, there being no such thing as free will in the composition of any human being that ever lived." - in Eruption. See also and especially “What Is Man?” for Twain's completely naturalistic view on human nature.
“Now, you receive all your ideas; therefore you receive your wish, you wish therefore necessarily. The word "liberty" does not therefore belong in any way to your will….The will, therefore, is not a faculty that one can call free. A free will is an expression absolutely void of sense, and what the scholastics have called will of indifference, that is to say willing without cause, is a chimera unworthy of being combated.” From The Philosophical Dictionary.
There are many other free will skeptics yet to be quoted, for instance LaMettrie, Hume, Mill, Locke, B. F. Skinner, and of course most modern-day philosophers and scientists who have weighed in on the topic, some of whom are mentioned here. If you come across any pearls of skeptical wisdom on free will by well-known thinkers, please be in touch.
TWC, March 2006
 Note that “infidelity” here means atheism.