Phenomenology is the methodology of Philosophical investigation. It demand an open-minded approach in our investigation of anything. The investigator begins by performing the "Phenomenological reduction" on himself. This means that in order to carry out an objective and reliable investigation he must get rid of all his previous ideas, preconceptions or presumptions about the object of his investigation so that he can carry out his investigation with a completely open mind, without bias,or prejudice. Having done that he then proceeds to perform an "eidetic reduction" on the object of his investigation by removing from it everything that is not part of the essence(nature)of that thing. Things like colour, size, weight, height, beauty or ugliness must be set aside, leaving only the essence( nature)of the object. The object can then reveal itself in its true nature to the unbiased mind of the investigator. The result of such investigation would be objective and reliable.. Other disciplines have adopted this Philosophical methodology of investigation. This book is a systematic study of this methodology, and it applies it to the study of Science, Social Sciences, Religion,History,etc