Throughout his professional life Steward carried on his
search for cross-culturally valid regularities. In effect, he
saw his anthropological mission as a search for causes. And
while he was appropriately cautious about spelling out laws
or ineluctable causes, he was not immune from the criticism
of those who dismissed the search for cultural regularities,
citing diffusion as an argument against Steward’s
evolutionary propositions. He responded to these objections
by drawing attention to the force of cultural ecological factors
in determining when, where, how, and if diffusion of
cultural items or artifacts could take place, thus making
diffusion an aspect of cultural evolution, a dependent rather
than an independent variable. Steward pressed on with his
search for what may be referred to as middle-range generalizations
or, more daringly, analysis and inference with predictive
potential.