Proof means evidence or justification to support an argument. Facts must be supported by facts. Having proof or arguments to support your facts, give them credibility. Evidence is needed to determine the truth of a proposition. Alcoholic proof is a measure of alcoholic strength of a drink. Artist’s proof is a single print taken during the printmaking process. Galley proof is a preliminary version of any publication. Proofreading is the act of reviewing an art work to check it for errors and make amendments or modifications, wherever necessary. In the words of Ayn Rand, “Achievement of your happiness is the only moral purpose of your life, and that happiness, not pain or mindless self-indulgence, is the proof of your moral integrity, since it is the proof and the result of your loyalty to the achievement of your values.”