QuestionsDoes life have a meaning?A life without a final end is not possible
Does life have a meaning?A given meaning

A life without a final end is not possible

The last end; every agent acts for an end; one cannot go on to infinity in ends

Thomas Aquinas 1225 · 1274Faith and reason cannot contradict each other.
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What it claims

There is a last end of human life, which everyone desires. For Thomas, it is what gives our acts their sense: a sense we find in our nature, not one we create.

Why

We always act for some end, and a chain of ends cannot go back forever: there must be a last one.

The same idea through history
Aristotle330 BCNicomachean Ethics, I, 2: if everything were wanted for the sake of something else, to infinity, our desire would be "empty and vain". There must therefore be an aim wanted for its own sake, which Thomas calls the last end.
Thomas Aquinas1271Questions 2 and 3 of the same Summa ask what this last end consists in (riches, honours, pleasure...) and conclude that it is seeing God. The present argument only establishes that there is one.
In short

"A life without a final end is not possible" is an argument by Thomas Aquinas (Summa theologiae, I-II, q. 1, a. 1 to 7 (1271), 1271) on the question "Does life have a meaning?" (answer: a given meaning). Its claim: There is a last end of human life, which everyone desires. For Thomas, it is what gives our acts their sense: a sense we find in our nature, not one we create. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P3). AskPhilosophy presents 4 objections, 0 of them with a documented reply, and the original text behind each premise, checked word for word.

Summa theologiae, I-II, q. 1, a. 1 to 7 (1271)
Valid with an implicit premise

Why do we do what we do? For a reason, which points to another reason, and so on. Thomas Aquinas asks whether this chain can fail to end. His answer is no: if nothing stopped somewhere, nothing would be desired and nothing would be begun. So there is a final aim of human life, wanted for its own sake, and it is what gives all the other aims their sense. For Thomas, this aim is written into our nature as creatures who will and choose. It is therefore given, not invented. This page presents only the proof that such an aim exists and that everyone desires it. What it consists in is another question, which Thomas treats next.

P1Properly human actions come from a deliberate will, and the object of the will is the end and the good. Therefore every human action is done for an end.
P2In a series of ends that depend on one another, one cannot go on to infinity. If the first term is missing, those that depend on it are missing too.
P3 · implicit premiseIf human actions are done for ends and there were no last end, the series of ends would go on to infinity: nothing would close it, and it could not simply turn in a circle either.
P4Whatever man wills, he wills for his last end. So everyone desires the last end, at least as his own fulfilment, even if they do not agree on what fulfils it.
Therefore there is a last end of human life, which everyone desires. For Thomas, it is what gives our acts their sense: a sense we find in our nature, not one we create.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P3, the computer finds a case where our actions have aims, where the series is not infinite, yet where there is no final aim: for example, several aims wanted for themselves that never meet.
Valid with P3. P1 says our acts have aims. P2 says the series of aims cannot be infinite. P3 links the two: without a final aim, the series would be infinite. We conclude there is a final aim. P4 adds that everyone desires it. Without P3, one can accept P1 and P2 and refuse to conclude: nothing then rules out a series of aims that stops without a final point, or turns in a circle. The last sentence of the conclusion (that this aim gives our acts their sense) is a reading of Thomas: the logic only establishes that a final aim exists.
Analogy. Someone looks for a book to lend it, lends it to please a friend, pleases a friend to be loved, wants to be loved in order to... At some point the question "why?" stops: because it is good to be loved, with no other reason behind it. If it never stopped, nobody would even have begun to look for the book.

Objections

4

Each objection is a conversation: click to see who replies and where the debate stands.

Jean-Paul Sartre, Existentialism Is a Humanism 1945 · attacks the conclusion

For Sartre, the aim of human life is not given in advance, because man has no fixed nature. He writes: "there is no human nature, because there is no God to have a conception of it". Man exists first and defines himself afterwards, and it is for each person to give his life a sense. If this is true, Thomas's last end is only a prejudice inherited from the idea that God thought man up as a craftsman thinks up a knife.

no reply
see the argument
No reply possible: objection raised in 1945, after the author's death (1274).
The debate goes on (our summary) Thomas died in 1274: he cannot answer Sartre. Our summary: the argument of q. 1 does not start from a divine concept of man, but from what a willed action is (a. 1, P1). Sartre does not deny, moreover, that each act has an aim: he writes that man is "what he wills" (§8) and that "it is yours to make sense of" life (§25). The disagreement is therefore about two points: is there a single last end common to all (Thomas), or does each person make his own project (Sartre)? And is this end discovered in human nature or chosen? See the argument "sartre-sens-a-creer".
Albert Camus, The Myth of Sisyphus 1942 · attacks the conclusion

Desiring a last end does not prove it exists. Camus writes: "The absurd is born of this confrontation between the human need and the unreasonable silence of the world." We thirst for meaning, and the world does not answer. That all men desire a fulfilment (P4) does not show that the world offers it to them.

no reply
see the argument
No reply possible: objection raised in 1942, after the author's death (1274).
The debate goes on (our summary) Our summary: Thomas's argument does not infer the existence of the last end merely from the fact that it is desired. It starts from the structure of action (a. 4): "if there were no last end, nothing would be desired". But it only shows that a last end is needed for there to be desire, not that the desire will be fulfilled: it is in the next questions (q. 2-3) that Thomas affirms that God alone can fulfil it. Camus accepts that a call exists and refuses to invent an answer to it. See the argument "camus-absurde-refus-suicide".
Baruch Spinoza, Ethics I, appendix 1677 · attacks the conclusion

Spinoza grants that men always act for an end, their own advantage. But he denies that nature itself has an aim: he writes that "nature has no particular goal in view" and that "final causes are mere human figments". We lend the universe the aims we have ourselves, because we do not know the true causes. A "given meaning" would then be a projection of our desire.

no reply
No reply possible: objection raised in 1677, after the author's death (1274).
The debate goes on (our summary) Spinoza was born in 1632 and Thomas died in 1274: the debate never took place. Our summary: Spinoza does not challenge P1 (our acts have ends), only that one concludes to an aim written into nature or willed by God. Thomas, on the contrary, ties man's last end to a God who orders it (q. 2-3), which Spinoza rejects as a prejudice. The question stays open: does an aim that everyone desires suffice to make a "given" sense, or is it only a fact about our psychology?
Thomas Hobbes, Leviathan, ch. 11 1651 · attacks premise 3

Hobbes denies there is a final aim: "there is no such Finis Ultimus, (utmost ayme,) nor Summum Bonum, (greatest good,) as is spoken of in the Books of the old Morall Philosophers". For him, "Felicity is a continuall progresse of the desire, from one object to another". Desire never stops: having reached one thing is only the way to the next.

no reply
No reply possible: objection raised in 1651, after the author's death (1274).
The debate goes on (our summary) Hobbes is aiming precisely at the "old moral philosophers" to whom Thomas belongs, but Thomas died 377 years earlier. In his text, Thomas writes that if there were no last end, "nor would the intention of the agent be at rest" (a. 4): he holds that the absence of a final rest would make action impossible, which Hobbes accepts as a description of life. The disagreement is clear: is a desire without end a successful life (Hobbes) or a "vain" desire (Aristotle, Thomas)?