Any progress in the theory of partial differential equations must also bring about a progress in Mechanics.
"Vorlesungen über Dynamik"
Wherever Mathematics is mixed up with anything, which is outside its field, you will find attempts to demonstrate these merely conventional propositions a priori, and it will be your task to find out the false deduction in each case.
"Vorlesungen über analytische Mechanik", ed. by H. Pulte in 1996
