That single thought is enough. The impulse increases to a wish, the wish to a desire, the desire to an uncontrollable longing, and the longing (to the deep regret and mortification of the speaker, and in defiance of all consequences,) is indulged.
Any who may wish to profit himself alone from the knowledge given him, rather than serve others through the knowledge he has gained from learning, is betraying knowledge and rendering it worthless