But we seem no closer to such laws [of human behavior] now, after several score more years of attempting to secure them, than Mill and his contemporaries were. The absence of such laws, or even of successively improved approximations to them, remains a continuing embarrassment to those empiricists who agree with Mill that the methods, and the sorts of knowledge which the application of such methods are to eventuate in, must be broadly the same in social and natural science. …

In fact he [Mill] is committed to the same variables in the explanation of human activity that Plato embraced in the Phaedo over two millennia before him. … Thus Mill's explanation [for lack of progress in terms of complexity of subject matter] is too weak in light of the allegation that no significant progress has been made in the provision of a real science of man throughout the whole of recorded history. No progress has been made in spite of the fact that throughout the period we have been acquainted with the explanatory variables presumably required to generate this science.