It&#x27;s actually not true to say that Schrodinger&#x27;s equation, or F=ma, cannot be derived.<p>This is because in order to derive something, you need to first start from a set of assumptions.  You can pick any assumptions you want, that is your privilege, as it is mine.  If you want F=ma to be an assumption, you can go on and derive things from that.<p>But truly, F=ma is not the most general assumption in theoretical physics.<p>If you look in any decent book on classical mechanics, you will find that F=ma in fact <i>is</i> derived from a much more general principle, the Lagrangian.<p>That is the same Lagrangian that is the subject of the OP, which is used to derive the Schrodinger equation; and it&#x27;s not just a coincidence.