ABSTRACT
Let's start simple. What controls, say, walking in humans? The standard view, which I expect you to agree with at this point, is that the explanation of both the universality of walking by humans and the variation in forms of it is relatively unprob lematical. It involves two distinct forms of cause. There is an underlying propensity for humans to walk due to the opera tion of an in-built genetic programme applying to all members of the species, being independent of learning, not based upon specific environmental events, and not dependent upon inter actions between internal and external factors. It is 'innate', part of 'nature'. There are, on the other hand, a variety of forms of walking to be observed, the variations being due to experien tial factors, shoes worn, fitness, load carried, cultural norms and so on, the 'nurture' side of the coin. Thus any given instance of walking can be accounted for by a consideration of the relative contribution of the two sorts of causal factors and their interaction. The same general argument applies to every human ability. It is a model for all development. It is the domi nant paradigm.
