This paper is a study of the fundamental viewpoints on Enkson's development theory. It is considered as follows : (1) The development of personality follows " inner laws of development" which is genetically innate to each person. It also follows "the epigenetic principle", that is, the principle of physical development. (2) Erikson puts the most importance on the reciprocity between a person and his environments in his theory. In this reciprocity, the environments should be guided by both the instinctive and the traditional patterns. (3) The components of healthy personality are considered eight pairs. Each pair is differentiated through time and when it becomes "phase-specific" (See the "chart"), it should find its lasting solution, through which the ego's essential strength is created. (4) Erikson assumes that the lasting solution of each pair is determined on the following three points indicated in the "worksheet". (1) What kind of environments a person interacts with (Radius of Significant Relations) (2) What sort of interactions he experiences (Psychosocial Modalities) (3) From the standpoint of Freud's psychosexual development, what part of the body zone takes the important role in the interactions (Psychosexual Stages) In conclusion, it is important to bear in mind that, according to Erikson's development theory, the growth of healthy personality presupposes the trustfullness in a healthy society.