Martin Heidegger

Martin Heidegger is a central philosophical interlocutor in Sartre’s analysis of consciousness and human reality, valued for his account of existence as a project toward possibilities yet repeatedly criticized for beginning without the cogito. Sartre’s engagement turns on a demand: care, worldhood, and futurity cannot be treated as structures of human existence unless consciousness makes them intelligible as such.

Heidegger’s existential starting point

Sartre contrasts Heidegger’s existential analytic with approaches that begin by examining the cogito. In Sartre’s account, Heidegger avoids the descriptive phenomenalism Sartre associates with Husserl and instead begins from Dasein, understood through an ekstatic project of its own possibilities. The project is not dismissed: Sartre accepts that human reality projects itself beyond itself. His objection is that Heidegger’s starting point has already deprived Dasein of the dimension of consciousness, which it cannot recover later merely by describing self-understanding.

This difference sets the terms of Sartre’s method. The cogito must serve as the point of departure, but it cannot be treated as a sealed, instantaneous truth. Sartre wants to start from pre-reflective consciousness and then show how it escapes the instant toward the totality of human reality. Heidegger’s analysis of existence matters to that project, but Sartre insists that an account of ek-stasis must arise from consciousness of ek-stasis; otherwise human reality risks becoming thing-like and blind, resembling the in-itself rather than a conscious relation to possibilities.

Care, possibility, and the future

Sartre credits Heidegger with defining human reality as care: an escape from itself toward the possibilities it is. He also accepts Heidegger’s claim that existence exceeds any isolated present. But he rejects any reading of the future as a representation held within present consciousness. A possibility becomes a person’s possibility only through consciousness’s movement toward it; without that relation, a system of possibilities would fall into the unconscious and thereby into the in-itself.

The tennis-court example makes the argument concrete. A position assumed while returning a ball gains its meaning from the movement that follows, not from a clear representation or a firm act of will. The future motion hovers non-thematically in the background, linking and modifying the present position. Sartre generalizes the structure to writing, smoking, drinking, and resting: conscious states take their meaning from a future beyond them. Heidegger is therefore right that Dasein is more than it would be if confined to the present; Sartre’s qualification is that this surpassing must be explained through consciousness, rather than installed as a structure that precedes it.

Sartre likewise resists turning the future into a not-yet-existing present or into a static container of time. The future is what the for-itself has to be precisely in that it cannot simply be it. As a lack, it draws the present beyond its current being; the present is a flight toward a possible self at a distance. This account preserves Heidegger’s emphasis on futurity while locating its force in the for-itself’s conscious, incomplete relation to itself.

Temporality and the world

Sartre’s disagreement also concerns how the past and future belong to human reality. He questions accounts that grant the past an existence of its own but do not explain how it can act upon or return into the present. He considers Bergson’s past, which remains in its place while ceasing to act, and Husserl’s retentions, which preserve earlier consciousnesses within the present. Against both, Sartre argues that an instantaneous cogito cannot reach beyond itself by these devices. His criticism of Husserl’s theory of time is paired with a wider concern about the limits of a consciousness conceived as unable to transcend itself toward world, future, or past.

For Sartre, Past, Present, and Future have no independent ontological priority: each conditions the others. He nevertheless emphasizes the present as the disclosure through which the for-itself lives its past as something it must surpass and its future as a lack that haunts it. Temporality is not a universal time imposed from outside, nor a separate being; it is the internal structure of the for-itself as a being that nihilates itself. This account retains the force of Heidegger’s temporal analysis but redirects the explanation toward consciousness’s relation to its own being.

Heidegger’s account of the world also becomes a point of correction. Sartre borrows the idea that the world is that in terms of which human reality makes known what it is, but argues that this disclosure is non-thetic rather than an explicit act of self-interpretation. In the circuit of selfness, a thirsty person’s possible satisfaction is not an object consciously represented as a future state; it is lived through a directed relation to a glass that appears as something to drink from. The world is “mine” in this indirect sense: it is haunted by possibilities that give it unity and meaning, though it is not explicitly known as mine in pre-reflective consciousness.

The same correction shapes Sartre’s account of instrumentality. Things appear within a network of tasks and purposes, and the totality of instruments corresponds to the possibilities of the for-itself. Sartre argues that being-in-the-world is not simply an escape from the world toward oneself: through action, human reality is referred from instrument to instrument and toward a beyond-the-world, the future world. A reflective turn would be required to make this worldly image an object for oneself. Thus the world is not a detached setting added to human existence, but neither does its meaning eliminate the need to account for the consciousness through which it is revealed.

Other people and the limits of Heidegger’s categories

Sartre places Heidegger within a broader modern effort to escape solipsism. Philosophers seek a fundamental connection with the Other at the heart of consciousness, but, in Sartre’s view, preserve the idea that this connection is realized through knowledge. His discussion of Husserl clarifies the stakes: the Other appears as a constitutive condition of the world’s unity and objectivity, present not only in encounters with particular people but in the meanings attached to objects. Sartre’s criticism is directed at theories that make knowledge the foundation of the relation, rather than establishing the relation as a concrete feature of existence.

The distinction also clarifies Sartre’s treatment of everyday human relations. He calls the lie a normal phenomenon of what Heidegger names Mitsein: lying presupposes the liar, the Other, and each person’s existence for the other. The liar can understand the truth and the deception clearly while concealing the intention from the person deceived. Sartre contrasts this with bad faith, which is not simply an interpersonal lie transferred inward. It is a project within the unity of one consciousness, which hides a truth from itself; social being may present the situation in which bad faith is undertaken, but it does not infect a person from outside or turn bad faith into a state.

Contingency, death, and fundamental project

Sartre also engages Heidegger’s account of the passage from inauthentic to authentic existence. He connects that passage with the intuition that human existence is contingent: the for-itself is not the foundation of its being and appears to itself as an unjustifiable fact. Heidegger associates this disclosure with restlessness, the call of conscience, and guilt. Sartre accepts the importance of apprehending contingency but cautions against identifying it with guilt, and argues that Heidegger’s description carries an ethical concern even as it disavows one.

In Sartre’s later methodological discussion, he refuses to treat a subject’s stance toward death as the final explanation of that subject’s fundamental project. Angst before death, resolute decision, and flight into inauthenticity are intelligible only against an original project of living; they do not themselves disclose the deepest choice. The inquiry must proceed beyond Heidegger’s interpretation until the projected end appears as the subject’s very being. Sartre’s account finally defines the for-itself through lack and freedom: possibility appears as what it lacks, value as the totality of being it lacks, and freedom as the concrete mode of that lack. Heidegger thus remains indispensable to Sartre’s vocabulary of care, temporality, and authenticity, while Sartre’s revisions insist that these structures be grounded in conscious, situated existence.