Adults have characterised infants as incompetent in action and cognition. An alternative interpretation which characterises infants as different rather than deficient is asserted. This alternative explanation is derived from an analysis using the formal categories of standard propositional logic. The analysis provides a structure within which all cognitive differences can be formally defined. The thesis suggests that formal characterisation is a necessity if progress is to be made from behavioural descriptions to cognitive explanations. The resultant interpretation is affirmed as an initial attempt towards a cognitive explanation of the mental world of the infant.