As my current work leaded me to analyse existence from the systemic point of view, I've decided it's time to read Sartre and about existentialism, which I've long time postponed. So I've started with Nausea and Existentialism is Humanism.

Minutes after starting, I've found Sartre is brilliant, but for creating mental melodramas. I couldn't finish reading, despite the small truths and lovely phrases, I see a global fallacy, a rhetoric construction, the same stuff humorists do, but excluding humour. Hope being wrong and finding the vein that will help me understanding Sartre.

What I don't get is Sartre builds the full exposition body based on implicit assumptions. What is the formal definition of existence, God, (human) essence, for Sartre, for existentialists? Can anyone give me some hints about this three concepts on existentialism?

  • Sartre is inverting a specific trope in classical philosophy: essence before existence; instead he says, existence before essence; ones essence is a creative activity that one must create. Commented Nov 8, 2016 at 6:15

5 Answers 5


I don't think that Existentialism is an artistic affectation, or 'a mood', nor even that it is particularly subjective. But its objectivity is psychological. It can be achieved only by visiting a lot of emotional states that humans share and building an understanding, rather than starting from a conceptual summary.

The whole approach looks back at older philosophy and notes that most formal definitions take place in bad faith. So there is a good reason for Sartre, or anyone representing him never to answer your question. And I am not even going to try.

Good faith requires negotiation of the situation, so setting an understanding down in stone is simply manipulation done beforehand. What you consider melodrama is meant to be an honest picture of human thought in extreme circumstances, where these negotiations have urgency. (Only the objective circumstances in which they take place conspicuously lacks actual urgency, so we are watching real life in slow motion.)

As a mathematician and an engineer, used to getting to the point quickly, I also find him exhausting to read. It is annoying to be pushed back and forth by his scenarios and negotiations, but that just means that people like us are withholding the patience that we would easily afford someone who wrote the way we like. That does not make our bad taste his flaw.

What you don't get is that all human interactions are based on implicit assumptions, even those that pretend otherwise. Philosophy is a human interaction. So get used to it, instead of putting a value judgment on an inescapable fact of life.

  • upvote about the definition, but don't agree about your ending: the implicit assumption is causality, and ontop of it we build our knowledge. Taking the whole body of discussion as an assumption is OK for religion, but not for philosophy. We need a logic infrastructure based on causality. In this case, I still need the concept of existence on existentialism: Is existence thinking? is it experiencing society? Having a physical volume? Persisting in time? Interacting with others? Loving? Otherwise, existentialism is a religion.
    – RodolfoAP
    Commented Nov 5, 2016 at 4:36
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    I don't care if you personally accept the last sentence. It is true for Sartre, and that is what matters, since that is the context here. If definitions are negotiated, a la Wittgenstein/de Sassure/Lacan, who are sources for Sartre, then you know existence when you see it. If it helps, it is human existence and not other existence that he is talking about. So you could say existence is consciousness, but how would that improve anything?
    – user9166
    Commented Nov 5, 2016 at 5:01
  • And you don't get to define what is a philosophy, the philosophical community does, so no one cares whether you think this is not a philosophy. The same standard would rule out a number of prominent thinkers, including Nietzsche (what is power, after all) and probably Heidegger (what is experience) By my standards, it surely does not have enough content or tradition to be a religion.
    – user9166
    Commented Nov 5, 2016 at 5:02
  • "so you can say existence is consciousness" then (causality) --> consciousness precedes essence. I reserve my opinion, since apparently I'm wrong and should follow what the philosophical community does, ad populum. Thanks anyway for addressing me on your answers, ad hominem, but I prefer keeping objective.
    – RodolfoAP
    Commented Nov 5, 2016 at 5:34
  • OK, if you are free to dismiss the opinions of anyone you choose, including Sartre, and everyone who studies him, then you should be less of a jerk when equally dismissive assertions are presented to you. If you were objective, you would see that. So if you are going to keep objective, maybe get there first.
    – user9166
    Commented Nov 5, 2016 at 15:12

As a phenomenologist, Sartre does not aim at arguing ( argument may prove anything) , but at describing the phenomena, what shows itself in a compelling fashion. In ordre to assess Sartre's philosophy, you cannot limit yourself to Existentialsme est un humanisme, but need to read L'Etre et le néant ( with a good guidesuch as Gardner's).

Short answer to this :

"What is the formal definition of existence, God, (human) essence".

Existence is precisely the mode of being of a being that has no definition, no essence. Hence, existence is " the being of nothingness" .

  • 3 historical stages in the constitution of the concept of existence :

(1) Existence as actuality , or being actually, not simple being potentially (traditional aristotelian ontology)

(2) Existence as actuality of a finite being ( etymologically) standing out (" ex") of its causes ( Monothesitic theology for which God *is a being * but does not " exist")

(3) Existence as actuality of a finite being that is not a "thing" , a natural being ( having an essence), a subject or substance bearing properties --> existentialist concept of existence

  • or, in Kierkegaard's words, actuality of a being that is neither eternal ( infinite) , neither in time understood as mere succession of identical " nows" ( the time of existence being the " instant")

  • or, in Heidegger's words , existence is the mode of being peculiar to "Dasein" for whom being is not " being this" ( having an " essence" , a " quiddity") but " having to be ( oneself)" in such a way that " its essence lies in its existence" ( contrary to God whose existence lies in its essence).

Note : to exist, in the existentialist sense, is not to be a " man" ; there is a conceptual difference between " Dasein" and " man" for a man is a natural being, a living being belonging to a species, etc, with a nature, etc.

  • 3 features of existence in the third sense

a) ipseity : an "existant" ( a being that " exists") is a self ; as says Heidegger , Dasein is this being that is always and everytime mine ; to exist is to be a " who" not a " what" ( an instance of a universal model);

b) facticity ( being thrown in the world, having being as a given, as a fact , in a given situation)

c) transcendance or " project" : being able to go beyond one's situation , to define oneself freely through one's own life plan and actions , to direct oneself towards being-possibilities

Link : https://plato.stanford.edu/entries/existentialism/#FacTra

  • According to Sartre, existence is a mode of being that violates the principle of non-contradiction : the " self" or "for-oneself" ( " pour-soi")

" is what it isn't, and is not what it is" ,

for the self cannot be anything whithout being aware of being such; but as a " self watcher" can never be perfectly identical to the self whereof he is aware; consciousness implying the invisible distance of " negation " or " nothingness".


Precisely: his rhetoric is exactly what humorists do. Existentialism is a mood - the world according to Sartre, Camus, etc.; how they choose to view and order the world. One can be an existentialist at breakfast, a Marxist at lunch and an Platonist at dinner with equal epistemic merit: none. Sartre presents his weltanschauung not an hypothesis. Would you ask of Richard Pryor his formal definition of social ontology?

To answer your questions, you could read all his writings, the writings of other existentialists and get a historical sense of his circumstance and yet your answer would be a matter of agreement or disagreement, not the confirmation of hypothesis.

Towards an understanding of Sartre's thoughts on existence, God and essence, you might like this 1946 public lecture by him.


For Sartre, essence of a man is everything he can currently know or judge about himself, it is "who/what/how I am", it is simply (current) self-concept or self-awareness - a reflective understanding.

Existence for Sartre is the current choice (of a possibility, which brings in meanings and attaches it to the essence) made by a man pre-reflectively, plus the immediately following reflective opening that (by virtue of the choice) he has broken away from his essence and is no longer what he "is"; it is the intuition that what I am is actually what was, and that this my essence is a pursueing demander, not a sanctuary. Here Anxiety stems from. It also stems from the fact that the freely selected choice does not be, it is only about a possibility, therefore it isn't a sanctuary either. That's Sartre's structure of existence as what always runs a step ahead of essence. That advancing is what produces true time, i.e. temporalizes one's experience. (True or "primeval" time shouldn't be confused with psychological time, of which objective physical time is only a logically "rectified" subtype.)

So, in short, and how I understand Sartre, existence is the process of how I appear not what I am, or turn out to be unequal to myself. As we know, the lack of identity with any state/status (being) in man was Sartre's principal idea.

See also Sartre on essence question.


This is the right question to ask and is the question Sartre tried to answer. The following is a formal answer, albeit a little abstract:

The core axiom of the philosophy is EXISTENCE = TRUTH. That is, saying that something is true is strictly synonymous to saying it does exist. Therefore what we know about existence is what we know about truth and vise versa, and we know nothing about it which creates anxiety. This is "exactly" equivalent to say Existence is unknown <=> Existence is meaningless <=> it has no essence <=> existence precedes essence which exactly answers your question. ( It can be shown this implies there exist a unique element that does not belong to any set, namely existence). This is why you will never understand what existence is by reading Sartre.

  • My distillation of philosophy is quite contrary as ur axiom, for me EXISTENCE != TRUTH. Existence is like in math we need to first make sure some object or relation exists before engineering to compute it in detail later. But in life as in philosophy, there're too many levels and types of existence so that we are lost in this mutli-level existence maze. Thus for me the core implicit axiom of philosophy should be to seek ontological truth only as in physics fashion, so that we can become clear about those dream-like illusions and colorful while confusing phenomena simply reflected from truth... Commented Mar 8, 2021 at 18:46
  • Let me clarify. In philosophy, existence is understood "in all generality". The verb “to exist in” is not the same as the verb “to exist”, the former (used in maths) is a predicate, the later (used in metaphysics) is not. For instance, a solution “x” exists for a differential equation means “x” verifies some formula, hence I have learned sth about “x”, namely that it is the solution of some differential equation. A pen exists in my bag tells me a property of that pen, it is present in my bag. However, in philosophy, “x exists” does not tell anything about what “x” is.
    – NOTT
    Commented Mar 9, 2021 at 21:51
  • Also, Truth in philosophy meant "the thing that cannot be refuted" or equivalently the "unnegatable". Whereas in maths “to be true” is not to imply a contradiction which is a quality of a statement not of an object, so “x is true” does not mean anything in maths unless x is a statement such as: x is (1+1=2).
    – NOTT
    Commented Mar 9, 2021 at 21:51
  • There exists a translation between math and philosophy: all you need is to replace existence by “existence in” and truth of an abject by truth of statement. You get again the equivalence Existence=truth. In fact, a statement “exists in” a theory if and only if it is “true in” that theory. (a theory is a set TH of formulae such that a statement S is in (i.e. exists in) TH iff TH proves S (i.e. S is true in TH), and Mathematics is a theory, hence the result).
    – NOTT
    Commented Mar 9, 2021 at 21:51
  • An interesting thing in philosophy compared to math/science is under different schools of thought, same thing can be both existent and non-existent, such as the "pen" in ur bag. Under mereological nihilism or reductional physicalism it's just some arrangement of simples (atoms) thus pen as a composite is not real substance, does not exist in these philosophies, similar conclusion under nominalism, platonic or leibniz panpyschic idealism, etc, while under realism, functionalism, emergentism, materialism as widely held by most laypeople that "pen" does exist. And math cannot help in this case... Commented Mar 9, 2021 at 22:37

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