perfectibility n 1: the capability of becoming perfect; "he believes in the ultimate perfectibility of man" [ant: {imperfectibility}]
perfectability \perfectability\, perfectibility \perfectibility\n. The capability of becoming perfect; as, he believes in the ultimate perfectability of man; -- usually spelled perfectibility. [WordNet 1.5]
Perfectibility \Per*fect`i*bil"i*ty\, n. [Cf. F. perfectibilit['e].] The quality or state of being perfectible. [1913 Webster]