is a filter whose response at a specific instant is independent of subsequent values of the excitation More precisely, an initially relaxed digital filter in which x(nT)=y(nT)=0 for n<0 is said to be causal if and only if
Answers to questions of the form 'wherefore ?' or, more vulgarly, 'how come ?' involve causality cf teleological Of or related to something that occasions or effects a result
If there is a causal relationship between two things, one thing is responsible for causing the other thing. Rawlins stresses that it is impossible to prove a causal link between the drug and the deaths