Was Helmholtz a Bayesian?

Modern developments in machine vision and object recognition have generated renewed interest in the proposal for drawing inferences put forward by the Rev. Thomas Bayes (1701 - 1759). In this connection the epistemological studies by Hermann Helmholtz (1821 -1894) are often cited as laying the foundation of the currently popular move to regard perception as Bayesian inference. Helmholtz in his mature writings tried to reconcile the German idealist notions of reality-as-hypothesis with scientists' quests for the laws of nature, and espoused the view that we attain knowledge of the lawful order in the realm of the real, but only in so far as it is represented in the tokens within the system of sensory impressions. His propositions of inferring objects from internal sensory signals by what he called 'unconscious inferences' have made Helmholtz be regarded as a proto-Bayesian. But juxtaposing Bayes's original writings, the modern formulation of Bayesian inference, and Helmholtz's views of perception reveals only a tenuous relationship.