The recursion procedure in cs is such a powerful tool. WIth it, you begin to see the divergence of computational ability of humans from machines. As the prof so rightly explained, the trick to recursion is just to blackbox the entire expansion part (in racket, (procedure (rest list)) or equivalent- and just assume that it works. If it does, then how should you manage it. Try to expand it out for even the most simplest procedure, and its a nightmare.
Thinking about the use of vector calculus in electricity and Magnetism, what is really going on is the summation of a lot of discrete quantities. At the root of a lot of theorems lies the idea of dq, or dV, or dW, the infinitesimal charge, potential or work present. The rest is just a few ways to add them all up- to sum them, essentially, and derive macroscopic scales of things.
But on that note,the difficulty of modeling biology is that biology does not occur in recurring components to be summed up easily. Every change in amino acid leads to a new protein, with different activation energies and surface charges. The trick to modeling biology is in statistics, because with it you are able to extrapolate non-identical behavior into some larger level of order. Hopefully.
-Aside note, the prof for E and M did an interesting demonstration of charging physical objects, using a fast motion to steal electrons from tape to tape, and showing that they attract each other. Then hold them to a giant conducting surface- the windsill, allow electron transfer- voila, they no longer attract. Demonstration that E and M actually pertains to reality. Wonderful lol.