In this lecture, a start is provided by explaining the general theory of nonlinearity of elasticity. The lecturer explains that it is his belief that the best way to start is to know the most general theory, being a 3D structure, before moving to more specialised structures such as 1D because one may have already used a series of assumptions to reach that specialised state.

A comparison is made between nonlinear theory and linear theory (at 0:06:47 in the video). The two different methods for solving nonlinearities in the geometry of a structure are introduced starting from 0:16:39 in the above video. The Lagrange method (a material method) is treated in this course because it is applicable to solids.
A recap of the statics of a stress tensor is presented at 0:39:05, after which the governing equations and manners of solving them using the principle of virtual work are introduced starting at 1:03:15.