>And if you think there
>are a priori philosophical truths, such as that time, space, and causality
>are necessaty conditions of knowledge, or every effect has a cause, then you
>might think these are derived from nonempirical sources.
Without entering this debate (I've already tarred myself with the practical humanist brush, after all) - for it could go on forever without making anyone the wiser (indeed is doing just that), effects do have causes, mate. This ain't a philosophical statement, it's a semantic necessity, no?
Cheers, Rob.