A maxim is a ground rule or subjective principle of action; in that sense, a maxim is a thought that can motivate individuals.
Maxim - Generally any simple and memorable rule or guide for living, for example 'neither a borrower nor a lender be'. Tennyson speaks of 'a little hoard of maxims preaching down a daughter's heart (Locksley Hall), and maxims have generally been associated with a 'folksy' or 'copy-book' approach to morality. - Oxford Dictionary of Philosophy
In deontological ethics maxims are understood as a subjective principle of action. An act is called moral if it has a certain universal value. In Immanuel Kant's categorical imperative, for instance, the maxim is combined with a certain intention to become moral. The moral intent is that one can, at the same time, will the subjective principle of action to become a universal law.
"Act only according to that maxim whereby you can, at the same time, will that it should become a universal law."
Michael Polanyi in his account of tacit knowledge stressed the importance of the maxim in focusing both explicit and implicit modes of understanding. “Maxims are rules, the correct application of which is part of the art they govern....Maxims can only function only within a framework of personal (I.e.experiential) knowledge”.