“Is it unreasonable then to expect, that some man possessed of the loftiest genius, coupled with ambition sufficient to push it to its utmost stretch, will at some time, spring up among us? And when such a one does, it will require the people to be united with each other, attached to the government and laws, and generally intelligent, to successfully frustrate his designs.”

Often the portion of this passage on "Towering genius..." is quoted without any mention or acknowledgment that Lincoln was speaking of the need to sometimes hold the ambitions of such genius in check, when individuals aim at their own personal aggrandizement rather than the common good.
1830s, The Lyceum Address (1838)
Context: It is to deny, what the history of the world tells us is true, to suppose that men of ambition and talents will not continue to spring up amongst us. And, when they do, they will as naturally seek the gratification of their ruling passion, as others have so done before them. The question then, is, can that gratification be found in supporting and maintaining an edifice that has been erected by others? Most certainly it cannot. Many great and good men sufficiently qualified for any task they should undertake, may ever be found, whose ambition would inspire to nothing beyond a seat in Congress, a gubernatorial or a presidential chair; but such belong not to the family of the lion, or the tribe of the eagle. What! think you these places would satisfy an Alexander, a Caesar, or a Napoleon? — Never! Towering genius disdains a beaten path. It seeks regions hitherto unexplored. — It sees no distinction in adding story to story, upon the monuments of fame, erected to the memory of others. It denies that it is glory enough to serve under any chief. It scorns to tread in the footsteps of any predecessor, however illustrious. It thirsts and burns for distinction; and, if possible, it will have it, whether at the expense of emancipating slaves, or enslaving freemen. Is it unreasonable then to expect, that some man possessed of the loftiest genius, coupled with ambition sufficient to push it to its utmost stretch, will at some time, spring up among us? And when such a one does, it will require the people to be united with each other, attached to the government and laws, and generally intelligent, to successfully frustrate his designs.