To a large extent, in many cases, doubt can be said to have a great influence in the pursuit of acquiring knowledge. In order to construct a balanced answer to this question, a rigorous evaluation of several key terms should be undertaken. The term “Doubt” can be defined as a feeling of hesitation regarding the legitimacy of something that is being alleged. A “key” can be seen as a tool that allows access to a more advanced place of meaning, in this case knowledge. The profound figure, René Descartes, who is often considered the "father of modern philosophy", called the "existence of mind" the "only absolute certainty in the universe". Descartes arrived at this conclusion through rational doubt. When an element of doubt is inherited, a pattern is thus created as a means of determining whether the information offered is actually true or not. Nevertheless, whether "doubt" is representative of "the key" in authenticating or aiding our habitual quest for knowledge or whether it actually constitutes a constraining deterrent on our thirst for knowledge depends on the specific aspect of knowledge examined. For the proverb in question, I will evaluate History and the natural sciences. In these areas of knowledge, there are many examples in which "accurate" information has been leaked out of skepticism, namely: theoretical developments within the natural sciences as well as the revision of historical revelations. The Persian proverb takes a definitive position as "the" only "key" to knowledge, but this statement must be challenged because in many cases doubt is only a tool in the acquisition of knowledge. An immediate contradiction to the Persian proverb is the idea for sure...... middle of article ......on Earth science: from continental drift to plate tectonics. Clarendon Press, Oxford.- James P. Levy, Appeasement and rearmament: Britain, 1936-1939, Rowman and Littlefield, 2006- Miller, R. 1983. Continents in collision. Time-Life Books, Alexandria, Virginia. Electronic sources: - http://www.aerospaceweb.org/question/history/q0162b.shtml (accessed January 26, 2011) - http://plato.stanford.edu/entries/ popper/ (accessed January 26, 2011) - http://www.ucmp.berkeley.edu/history/wegener.html (accessed January 26, 2011) - http://en.wikipedia.org/wiki/Michael_Shermer (accessed January 26, 2011) - http:/ /en.wikipedia.org/wiki/Michael_Shermer (accessed January 26, 2011) - http://en.wikipedia.org/wiki/Alex_Grobman (accessed January 26, 2011) - http://en.wikipedia.org/ wiki/Doubt (accessed January 19, 2011) - http://www.wisegeek.com/what-is-continental-drift-theory.htm (accessed January 26 2011)