Nomothetic Causality

Nomothetic causality is often used in social research. Nomothetic causality refers to a more generalized understanding of something as compared to idiographic causality which focuses more on detailed and in-depth understanding. In order for nomothetic causality to hold true, three criteria must be met. First, the variables being looked at must be correlated. Second, the variables must be non-spurious  meaning their occurrence cannot be accounted for by the presence of a third variable. Finally, the cause must take place before the effect in order for nomothetic causality to exist. Because nomothetic causality focuses more on generalizations, and studies only a small set of causal factors, it is highly probabilistic in nature. Another interesting fact about this form of causality is that exceptional cases to a set pattern cannot be used to disprove a causal relationship. Thus, even though it might be possible to find one or two exceptions to the rule, nomothetic causality would focus more on the general pattern than on the one or two cases that fall outside of the particular pattern.

http://en.wikibooks.org/wiki/Social_Research_Methods/Research_Design
http://books.google.com/books?id=koFuKlfodWsC&pg=PA93&lpg=PA93&dq=nomothetic+causality&source=bl&ots=xiNkElfEN1&sig=Vqqjg0Km-Ncg2SmL_kCwDc7Pjws&hl=en&sa=X&ei=7HBbUYW4JIf0iQLMrIHACg&ved=0CE8Q6AEwAw#v=onepage&q=nomothetic%20causality&f=false