Erikson is rather vague about the causes of development. What kinds of experiences must people have in order to successfully resolve various psychosocial conflicts and move from one stage to another? The theory does not have a universal mechanism for crisis resolution.
Indeed, Erikson (1964) acknowledges his theory is more a descriptive overview of human social and emotional development that does not adequately explain how or why this development occurs. For example, Erikson does not explicitly explain how the outcome of one psychosocial stage influences personality at a later stage.
One of the strengths of Erikson's theory is its ability to tie together important psychosocial development across the entire lifespan.