[Kamepherype]

If I were rewriting the DE I would break up Fi x Fc differently.

I would have a (Fraction of planets with life that develop complex, multicellular animal life). It seems to me that this is an important, non-trivial step, and at least potentially could be treated in a semi-rigorous factor. It would describe factors like the length of time that a planets surface remains tectonically active (if you hold to the importance of that, as described by Ward & Brownlee).

I'd also be tempted to then just combine the remaining (Fraction of planets with complex, multicellular animal life that develop intelligent life) and Fc into a single number. It's always bothered me that "intelligent life" is a somewhat arbitrary cutoff for a species, and "radio telescopes" is a somewhat arbitrary cutoff for a culture, so I don't see why you need two arbitrary points just to mark some nature/culture divide. That's a rather secondary issue though.