Subjectivity, Bayesianism, and Causality

Bayesian probability theory is one of the elementary frameworks to model reasoning under uncertainty. Its defining property is the interpretation of probabilities as degrees of belief in propositions about the state of the world relative to an inquiring subject. This essay examines the notion of subjectivity in Bayesian probability theory. It turns out that the assumptions about subjectivity have a long tradition in Western culture that lie at the heart of its belief system, political organization and intellectual discourse. As an example, I show that some basic concepts of Bayesian probability theory have a counterpart in Lacanian theory. Furthermore, Lacanian theory explains agency in terms of an interruption of the signifying chain of the subject performed by the so called "objet petit a", which turns out to have striking similarities with causal interventions in statistical causality. Finally, an abstract model of subjective interaction is introduced that accommodates causal interventions in a measure-theoretic formalization.