Originally Posted by **kiwiheretic** See (attached) how the Lagrangian really was only formulated for T (kinetic energy) but by assuming conservative forces only they were able to do some hocus pocus and invent some terms (namely the time derivative of the potential) which must be zero for conservative forces so that they could make the equation "look" more symmetrical and replace the T with an L. |

Where are you getting this "time derivative of the potential" from? It's not in the page you posted. And its not hocus pocus in anyway and the generalized force doesn't have to always be zero since not all forces are conservative. The potential is introduced only in situations when the force is conservative, i.e. is the gradient of a potential function.

When the force is magnetic then one uses what's known as a velocity dependent potential, U, in the Lagrangian which is a more general potential. The Lagrangian is the expressed by L = T - U r(rather than L = T - V). In such cases Lagrange's equations still work.

Originally Posted by **kiwiheretic** My question is is this not a bit disingenuous? |

Absolutely not.

Originally Posted by **kiwiheretic** Is "Action" a real thing or just a mathematical contrivance which only works for conservative forces (and not magnetism)? |

I don't know what you mean by "real thing." Please clarify.

Action is an integral. Where does your question come from? It doesn't appear to be connected to the page you posted.

I recommend reading more about the concept of action. See

https://en.wikipedia.org/wiki/Action_(physics)

I recommend finding

**Classical Mechanics - 3rd Ed** by Goldstein, Safko and Poole on this subject. You can download it from here:

http://booksc.org/book/2059463/88e59f
That might be an earlier edition though. But it doesn't matter since the relevant chapter will be the same.