Articulacy in human experts is encountered only in those few skilled tasks where explicitness is of the essence. In such cases suitable bodies of decision rules have been hand-crafted so as to construct in computer memory commercially viable expert systems. A need for more radical automation of systems construction arises in the commoner case that the skill is intuitive. No explicit codification of 'how to do it' can then be directly prepared. If however computer programs can be written which will so analyse the inarticulate expert's actual decisions as to extract a rule-based model of his skill, then automated synthesis of expert systems can be developed as a branch of software manufacture.