“They can because they think they can.”
Aeneid (29–19 BC), Book V
Source: Aeneid (29–19 BC), Book V, Line 231 (tr. John Conington)
Possunt, quia posse videntur.
“They can because they think they can.”
Aeneid (29–19 BC), Book V
“They can because they think they can.”
Source: Translations, The Aeneid of Virgil (1866), Book V, p. 153
“Because I'm the CEO, and I think it can be done.”
                                        
                                        On why he chose to override engineers who thought the iMac wasn't feasible, as quoted in TIME magazine (24 October 2005) 
2000s
                                    
                                        
                                         Message to Linux kernel mailing list, 2006-09-22, Torvalds, Linus, 2008-06-07 http://lkml.org/lkml/2006/9/22/319, 
2000s, 2006
                                    
Dilbert blog, My day as a Neanderthal, 2006-10-25, http://web.archive.org/20061107115218/dilbertblog.typepad.com/the_dilbert_blog/2006/10/my_day_as_a_nea.html, 2006-11-07 http://dilbertblog.typepad.com/the_dilbert_blog/2006/10/my_day_as_a_nea.html,
“The greatest of all mistakes is to do nothing because you think you can only do a little.”
                                
                                    “Fortune assists the Bold, the Valiant Man
Oft Conqueror proves, because he thinks he can.”
                                
                                
                                
                                
                            
                                        
                                        Fab. LII: Of the Forrester, the Skinner, and a Bear, Moral 
The Fables of Aesop (2nd ed. 1668)