Since the topic of Lawvere paper is differential geometry, the Bernoulli is likely <A HREF="https://en.wikipedia.org/wiki/Jacob_Bernoulli">Jacob Bernoulli,</A> or his brother <A HREF="https://en.wikipedia.org/wiki/Johann_Bernoulli">Johann,</A> and refers to their calculus of variations and the principle of virtual work. Further evidence is this <A HREF="http://denise.vella.chemla.free.fr/Lawvere-categ-3.pdf">paper</A> by Lawvere on category theory, where he explicitly refers to Bernoulli in the context of the calculus of variations.