Baruch Spinoza

Baruch Spinoza is not presented here through a life story but as a recurring philosophical interlocutor in an argument about consciousness and human reality. Sartre invokes his account of ideas, possibility, psychic states, and determination, while repeatedly testing whether those accounts can explain phenomena that exceed static being. The resulting portrait is intellectual rather than biographical: Spinoza’s concepts give Sartre both a precise vocabulary and a series of positions against which to define his own ontology.

Consciousness and the reflecting-reflected structure

Sartre introduces Spinoza while examining consciousness of belief, a phenomenon that cannot be divided into two independent things: a belief observed from outside and a separate consciousness that observes it. Consciousness of belief is belief, yet belief is also consciousness of belief. The two are one being in absolute immanence, but an attempt to grasp that unity makes it slip into a play of reflection and reflecting. This is not a stable identity that can simply be held as an object; each term refers to the other, and each is distinct from it.

The difficulty leads Sartre to challenge explanations that insert infinity into consciousness. Spinoza’s idea of an idea, extended into an idea of an idea and onward, offers one way to explain the reflecting-reflected pattern. Sartre also mentions the Hegelian account of a return upon itself. He argues that such appeals to infinity fix and obscure the phenomenon, reducing consciousness to the mode of being of the in-itself. The alternative is a unity that remains dual: reflection is its own reflecting, rather than a self-contained unity that absorbs its difference into a higher synthesis. Treating consciousness and belief as a dyad does not solve the problem either, because it reinstates the infinite regress and misses pre-reflective consciousness, which is already self-consciousness.

Desire and the status of possibility

Spinoza also enters Sartre’s analysis of desire. Sartre rejects the attempt to explain desire as a physical conatus, or as a state running parallel to a physiological process. Deprivation of water, for instance, may produce positive changes in an organism, such as thickened blood; those changes describe an organism’s state, not a desire for water. If psychic thirst is identified with such a state, it becomes desire only in the eyes of an outside witness. For desire to be desire to itself, Sartre argues, it must transcend itself toward an object and exist as a lack of being. This account sets a limit on explanations that treat desire as a self-contained condition.

The debate over possibility makes the contrast more explicit. Sartre presents Spinoza’s position as treating possibilities as products of ignorance: as knowledge becomes complete, they disappear. On this view, possibility has the reality of a psychic mode, not a property belonging to the world. Leibniz offers a different account, granting possibles a place in divine understanding as systems of possible worlds. In that framework, it can be said that Adam might not have eaten the apple, because a different system of compossibles includes that alternative. Sartre argues that the two positions remain closer than they first appear: in both, the possible is thought rather than an unrealized property of beings.

Against these accounts, Sartre turns to ordinary experience of the sky. A statement that rain is possible does not merely report uncertainty or logical consistency; the possibility appears as a threat carried by the clouds, as their surpassing toward rain. Possibility belongs to beings as a way of exceeding their present state, whether or not that exceeding is realized. The contrast clarifies Sartre’s use of Spinoza: the issue is not simply whether possibilities can be conceived, but whether their being can be accounted for without reducing them to thought.

Reflection and psychic life

When Sartre asks how reflection can know a consciousness that is already past, he recalls the familiar model of reflection as a new consciousness directed toward the consciousness reflected on. He identifies this model with Spinoza’s idea of an idea. But if the reflective consciousness is autonomous, Sartre argues, it cannot later be reunited with the consciousness it knows. The two would remain separate existents, connected only externally; an image of the reflected consciousness would then replace the internal relation that reflective knowledge is supposed to explain. Sartre’s objection continues the earlier problem: treating reflection as another independent mental item does not account for the unity of consciousness.

Spinoza’s finite modes provide another comparison, this time for the way people speak of their feelings. A person says that a joy is theirs, as though the feeling were a detachable possession or visitation impressed upon the flow of time. Sartre does not dismiss the psychic duration built from such feelings, states, and acts as unreal. It is the proper subject matter of psychology, and it is the level at which concrete relations between people—jealousies, grudges, claims, struggles, and ruses—take shape. Yet this succession of psychic facts cannot define the being of the unreflective self: a joy cannot be required to be the sadness that came before it. Sartre distinguishes the lived unity that historicizes itself from the series of psychic objects through which reflection represents it.

That distinction is sharpened by Sartre’s account of the psyche. The Ego, with its grammatical forms of “I” and “Me,” is a transcendent psychic unity that includes states, qualities, and acts. Qualities are dispositions, such as irascibility; a state is an actual, contingent reality, such as hatred that persists after a particular action has provoked resentment. Some states can become constitutive of a person, as in Sartre’s example of Pozzo di Borgo’s hatred of Napoleon, but they remain different in kind from latent qualities. Acts, such as a boxer’s training or a scientist’s research, are synthetic arrangements of means toward ends. Spinoza’s picture of finite modes helps frame the problem of treating psychic life as a collection of such separable realities; Sartre uses the distinctions to show why that picture cannot replace the for-itself’s lived unity.

Determination, persons, and the limits of shared concepts

Sartre’s discussion of external negation revises a maxim associated with Spinoza: Omnis determinatio est negatio, or “every determination is negation.” Sartre’s example is a newspaper lying on a table. The newspaper does not itself deny that it is the table; the relation between the two leaves each thing unchanged. The determination that distinguishes the “this” from the “that” belongs neither to object as an intrinsic feature nor to a subjective phantom. It is an ideal negation, unlike the internal negation through which the for-itself relates to being. Sartre thereby preserves the force of Spinoza’s formulation while restricting what it can mean: not every determination is a negation belonging to the being it determines.

Spinoza’s account of human nature also helps Sartre mark a limit in theories of the Other. A universal essence of humanity, Sartre argues, cannot determine the multiplicity of concrete persons; knowing what human beings share does not establish how a particular other person is possible as an object of experience. Sartre therefore turns to the Kantian question of the conditions that make experience of the Other possible, treating the Other as a particular phenomenon rather than a merely intelligible or noumenal reality. Spinoza’s system functions here as a comparison: a general account of human essence cannot by itself recover the irreducible plurality of actual people.

Significance in Sartre’s argument

Across these discussions, Spinoza is neither reduced to a foil nor simply adopted as an authority. His formulations expose recurrent philosophical pressures: how unity can include difference, how possibility can have being, how mental life relates to bodily states, and whether determination belongs to objects or to the relations through which they appear. Sartre repeatedly uses Spinoza’s concepts to make those questions exact, then resists answers that convert consciousness into an infinite chain, possibility into mere thought, or persons into instances of a universal essence.

The pattern gives Spinoza a structural role in the argument. His work marks several points where a theory approaches the phenomena Sartre wants to describe but, in Sartre’s judgment, makes them static or external in the effort to explain them. By distinguishing the for-itself from psychic objects and internal negation from external determination, Sartre develops an alternative account of lived consciousness without erasing the problems Spinoza helped bring into view.