Determinism

Determinism appears here as a scientific postulate whose meaning cannot be settled by treating the world as a system of relations among things alone. Sartre distinguishes the observer’s constitutive place in scientific experience from a claim that observation either proves or disproves determinism.

The postulate and its limits

The discussion rejects the idea that the observer can be removed from scientific relations without remainder. Drawing on microphysics, Sartre describes experience as a system of univocal relations in which the observer is not excluded. That inclusion is not a turn toward pure subjectivity: pure subjectivity, like absolute objectivity, would be an abstraction. The observer instead occupies an original relation to the world, a place toward which the relations under consideration are oriented.

Accordingly, Heisenberg’s uncertainty principle is neither an invalidation nor a validation of the determinist postulate. It cannot simply be taken as a verdict for or against determinism, because the scientific relation at issue already includes the human observer’s place in the world. The principle therefore complicates any account of science that imagines its laws as wholly detached connections between things.

Measurement and engagement

Sartre illustrates the role of an observer’s scale through the measurement of motion. A body moving toward another can appear a hundred times faster when examined with a microscope than when seen with the naked eye: in the same interval, it traverses a space a hundred times larger under the dimensions used in the microscopic observation. The moving body has not thereby approached its target more closely. Rather, the description of its speed depends on the dimensions against which movement is measured.

Those dimensions are not simply delivered by detached knowledge. Human beings decide them through their upsurge into the world, and they must do so for the dimensions to be there at all. Their relativity is thus not merely a property of what observers know; it arises from their prior engagement at the heart of the world. The example makes scientific measurement depend on a situated relation without reducing it to private opinion.

Relation, not relativism

The account links this situated measurement to the theory of relativity: an observer at the heart of a system cannot determine by experiment whether that system is at rest or in motion. Sartre insists that this relativity is not relativism and has nothing to do with the idea that knowledge makes truth arbitrary. He describes modern science’s relativity as directed toward being, not merely toward knowledge.

The larger consequence is that human reality and the world are relational beings. For the observer, coming into existence means unfolding distances from things and thereby causing them to be there as things at a distance. The world, in turn, refers that relation back to the observer. Determinism is therefore discussed within a framework that refuses both an observerless world and a purely subjective one: scientific relations are intelligible through the situated relation between human reality and the world, while the uncertainty principle itself settles neither the truth nor the falsity of the determinist postulate.