> I am sorry that I could not express the point clearly. Yes, it is a quote
> from _ Tom Sawyer_; "He had discovered a great law of human action, . . .
> that in order to make a man or a boy covet a thing, it is only necessary
to
> make the thing difficult to attain" (Ch.2).' The law is also mentioned in
> his other works. I would like to know if there are some essays that focus
> on Twain's thought of the 'law of human action just for reference.

Takashi Suzuki,

Try Forrest G. Robinson's _In Bad Faith: The Dynamics of Deception in
Mark Twain's America_ (Harvard U., 1986).  Or, for more in Twain's words,
the U. of Cal. edition of _What is Man? and Other Philosophical
Writings_.

And you express yourself well.
larry marshburne