Esoteric, Mesoteric, Exoteric
In common usage, esoteric means the inner or more advanced aspect of a spiritual teaching. Exoteric means the outer form of a teaching, one that is shown to the public. In 4th Way discourse, these terms are used in a more specific meaning.
Humankind is divided into 4 circles according to progress on the path of conscious evolution. The outer circle or exterior men corresponds to the default state of man and is not concerned with esoteric work. In this circle it is rare that any two individuals should precisely understand each other on any matter of consequence or complexity. All see the world through thick lenses of subjectivity and are subject to the confusion of tongues alluded to in the Babel story of the Bible.
The exoteric circle is the outermost circle of interior or consciously working man. The 4 Ways lead from the outer circle into the exoteric one.
The understanding of exoteric man is theoretical and contemplative, they know more than they can explain or put to practice but some degree of shared clarity starts to form there. The members of the mesoteric circle understand each other precisely and possess the information of the esoteric circle but are not capable of bringing this all to practice. The esoteric circle consists of the persons having attained the development possible to the human form. Their actions cannot be in contradiction with their knowledge and the same knowledge is clear to all members of this circle.
The central idea is that as man progresses, the world is seen with increased clarity. Therefore misunderstanding and ambiguity decrease along the way and actions become naturally aligned since all see the same world and become increasingly capable of acting on esoteric principles.
Gurdjieff says that the universe needs a group of conscious humans. A certain number of people must have attained the esoteric level by a certain time in order for a cosmic purpose to be fulfilled. The branch of the ray of creation corresponding to the Earth will otherwise wither and be wasted.