Observations on patients who lost visual imagery after brain damage call into question the notion that the knowledge subserving visual imagery is “tacit.” Dissociations between deficient imagery and preserved recognition of objects suggest that imagery is exclusively based on explicit knowledge, whereas retrieval of “tacit” visual knowledge is bound to the presence of the object and the task of recognizing it.

Based on neuropsychological evidence of nonverbal impairment accompanying aphasia, I propose that the neural prerequisites for language acquisition are shared with a range of nonverbal capacities. Their commonality concerns the ability to recognize a limited number of finite elements in manifold perceptual entities and to combine them for constructing manifold entities.