e.

HP: Now here we have the simplest form of the problem of
    the &quot;complexity of [the cell's] everyday phenomena&quot;,
    and the point is that in this case we know that there
    is no linear, one-at-a-time solution.  In other words,
    there is no logical form that describes folding. [Roughly,
    there is no computationally tractable ab initio folding
    algorithm, and approximations must rely on trial and error,
    multiple-level partial decomposability, and parallel network
    relaxation 