This post is based on an earlier one (in Portuguese) I wrote in the social network USP maintains.
It is based on an event that took place during a lecture of the discipline PMT2406-Mechanics of Metallic Materials, which is optional for the 10th semester (last) of the Metallurgical and Materials Engineering undergraduate courses at the Escola Politecnica da USP.
I was talking about a quite specialized subject, Deformation microstructures in fatigue, where I finish the discussion with the results of H. L. Huang, published about 10 years ago (for example, here).
It is a complex subject and, to my best knowledge, it is ignored by the fatigue community. I always felt justified, since I believe these results are very important.
I was finishing the explanation, so I needed a closure (no pun intended), so I said:
-"Why are you learning this?"
The few students, who were watching my explanation with full attention, looked at me in disbelief. I continued:
-"You will most probably neither hear something about this anymore, nor you will use this knowledge in the professional life."
If the students thought I was going crazy before, now they were sure. Before they could complain, I finished:
-"We learned the arguments, the mental processes the author used to reach these results."
I was doing this in real time, I am not sure if the students perceived this, or if they believed I planned that all along.
I felt relieved, I finally understood that what we teach is how to think about the subject and not the subject itself (in many cases the subject is only the tool in the learning process).
In my previous post I concluded realizing this explained why our students become excellent professional, even with the pitiful didactic most professors possess (myself included).
Here I want to extend a bit more. In the ECF20 I recently attended, there was a special discussion about teaching fracture mechanics. I remember one of the participants told that, instead of teaching how to use fracture mechanics in projects, he discussed how to derive the HRR field equations. I am sure he knows that this knowledge is not "useful" for the engineer, but he is interested in forming thinking engineers rather than automats.
For me these realizations are important, I finally got in peace with my teaching.