Descartes starts his Meditations off and thinks that he should doubt all of his senses, because he fears that they have been deceiving him ever since he has had them. He then proceeds to ponder on the true meanings of his own existence and if there was some higher power that led the world into its current state. Throughout his deliberations, he goes through all sorts of feelings as to whether God exists and if this "god" is a omnipotent and good god or whether this god would deceive the human race and skew their sensory perception. In everything Descartes goes through, it is clear that he uses a methodological and rational way of doubting the things that he does not know if he truly believes. He provides significant reasons as to why he doubts each point that he goes through. Descartes places all doubt in his own rational boundaries, and he always tries to keep this rationality in every argument that he dictates. If that statement is indeed true, then by the end of the book Descartes can truly see that some of his skepticism was not in fact rational, and so he says that "the hyperbolic doubts of the last few days ought to be rejected as ludicrous" (Meditations 89; pg. 58).
William of Ockham once said "do not multiply entities without good and sufficient reason". In the beginning of his Meditations, Descartes says that he has found some of his childhood beliefs to be false, and thus he thinks that all the thoughts and beliefs built upon those said beliefs would also have to be false. He feels the need to reevaluate his entire framework of thinking in search for a higher truth, and this is admirable. For one to call everything he/she knows into question, that person has to be fully able to accept his/her findings, no matter how hard those realizations might be. To some, that is a daunting task, but Descartes thinks that in this stage in his life, it is the right time for such an undertaking.