In our ongoing contest to find the longest sentence in Philosophy, careful reader Matthias Brinkmann alerts me to a new candidate — this 286-worder from Kant’s Practical Philosophy:
“Now, if ends must first be given to us, in relation to which alone the concept of perfection (whether internal in ourselves or external in God) can be the determining ground of the will; and if an end as an object which must precede the determination of the will by a practical rule and contain the ground of the possibility of such a determination — hence as the matter of the will taken as its determining ground — is always empirical; 
then it can serve as the Epicurean principle of the doctrine of happiness but never as the pure rational principle of the doctrine of morals and of duty (so too, talents and their development only because they contribute to the advantages of life, or the will of God if agreement with it is taken as the object of the will without an antecedent practical principle independent of this idea, can become motives of the will only by means of the happiness we expect from them); from this it follows, first, that all the principles exhibited here are material; second, that they include all possible material principles; and, finally, the conclusion from this, that since material principles are quite unfit to be the supreme moral law (as has been proved), the formal practical principle of pure reason (in accordance with which the mere form of a possible giving of universal law through our maxims must constitute the supreme and immediate determining ground of the will) is the sole principle that can possibly be fit for categorical imperatives, that is, practical laws (which make actions duties), and in general for the principle of morality, whether in appraisals or in application to the human will in determining it.” (Translated by Mary Gregor, Cambridge University Press, 1996, p. 173)
Thus, updating the list, we now have the seven wordiest as:
1. Kierkegaard: 330 words.
2. Locke: 309 words.
3. Kant: 286 words. Also 174 words. Also: 163 words.
4. Moore: 239 words.
5. Aristotle: 188 words.
6. Bentham: 164 words.
7. Mill: 161 words.
Forthcoming: Anoop Verma sent me a quotation from Ayn Rand’s philosophical fiction, which I will check out. Also Matthias Brinkmann in the same post raises the question of semi-colons, as clauses joined by semi-colons can become stand-alone sentences.
The last sentence on p. 96 of “Collectivized Ethics” in Rand’s The Virtue of Selfishness is 173 words long.
A while back I read Isaiah Berlin’s Political Ideas in the Romantic Age. I recall that it had some very long paragraphs, some going on for more than a page, but can’t recall if any for those was a sentence in itself. Berlin is fond of clauses, colons and semi-colons. I’m still in Australia and won’t be back in Canada for another week. When I get back, I’ll take a quick look through the book and see if I can find another entry for your interesting contest.
If not the longest one of my favorite is by Aristotle in, I believe, ‘On Interpretation’ introducing affirmative and negative propositions: “Now it is possible to state of what does hold that it does not hold, of what does not hold that it does hold, of what does hold that it does hold, and of what does not hold that it does not hold.”
I’m also fond of a very short one by Empedocles who claimed to “have already been in the past a boy [which I believe to be true] and a girl, a shrub and a bird and a fish which lives in the sea.”