One mutual goal of linguistic theory and learning theory is to determine wh
at kinds of parametric changes are possible (and which are more natural) in
human language. The present paper discusses implications of the syntactic
change evidenced in the history of Spanish for the minimalist approach to s
yntax, on the one hand, and the theory of language acquisition, on the othe
r. In particular, it attempts to characterize how the notion of economy may
be defined and characterized in diachronic investigation. In this connecti
on, it argues that the replacement of covert operations by overt operations
is compatible with a particular notion of diachronic economy and the langu
age acquisition process. The paper concludes that one-dimensional notion of
economy is not quite sufficient to capture the nature of natural language.