Law of three stages
The Law of Three Stages is an idea developed by Auguste Comte in his work The Course in Positive Philosophy. It states that society as a whole, and each particular science, develops through three mentally conceived stages: (1) the theological stage, (2) the metaphysical stage, and (3) the positive stage.
The progression of the three stages of Sociology
(1) The Theological stage refers to explanation by personified deities. During the earlier stages, people believe that all the phenomena of nature are the creation of the divine or supernatural. Men and children failed to discover the natural causes of various phenomena and hence attributed them to a supernatural or divine power.[unreliable source?] Comte broke this stage into 3 sub-stages:
- 1A. Fetishism - Fetishism was the primary stage of the theological stage of thinking. Throughout this stage, primitive people believe that inanimate objects have living spirit in them, also known as animism. People worship inanimate objects like trees, stones, a piece of wood, volcanic eruptions, etc.
- 1B. Polytheism - The explanation of things through the use of many Gods. Primitive people believe that all natural forces are controlled by different Gods; a few examples would be God of water, God of rain, God of fire, God of air, God of earth, etc.
- 1C. Monotheism - Monotheism means believing in one God or God in one; attributing all to a single, supreme deity. Primitive people believe a single theistic entity is responsible for the existence of the universe.
(2) The Metaphysical stage is the extension of the theological stage. Metaphysical stage refers to explanation by impersonal abstract concepts. People often tried to believe that God is an abstract being. They believe that an abstract power or force guides and determines events in the world. Metaphysical thinking discards belief in a concrete God. The nature of inquiry was legal and rational in nature. For example: In Classical Hindu Indian society the principle of the transmigration of the soul, the conception of rebirth, notions of pursuant were largely governed by metaphysical uphill.
(3) The Positivity stage, also known as the scientific stage, refers to scientific explanation based on observation, experiment, and comparison. Positive explanations rely upon a distinct method, the scientific method, for their justification. Today people attempt to establish cause and effect relationships. Positivism is a purely intellectual way of looking at the world; as well, it emphasizes observation and classification of data and facts. This is the highest, most evolved behavior according to Comte. 
Comte, however, was conscious of the fact that the three stages of thinking may or do coexist in the same society or in the same mind and may not always be successive.
Comte proposed a hierarchy of the sciences based on historical sequence, with areas of knowledge passing through these stages in order of complexity. The simplest and most remote areas of knowledge — mechanical or physical — are the first to become scientific. These are followed by the more complex sciences, those considered closest to us.
The sciences, then, according to Comte's "law", developed in this order: Mathematics; Astronomy; Physics; Chemistry; Biology; Sociology. A science of society is thus the "Queen science" in Comte's hierarchy as it would be the most fundamentally complex. Through social science, Comte believed all human social ills could be remedied.
Critiques of the law
Historian William Whewell wrote "Mr. Comte's arrangement of the progress of science as successively metaphysical and positive, is contrary to history in fact, and contrary to sound philosophy in principle."  The historian of science H. Floris Cohen has made a significant effort to draw the modern eye towards this first debate on the foundations of positivism.
- ""What Are the Major Contributions of Auguste Comte to Sociology?"". PreserveArticles.com: Preserving Your Articles for Eternity. Retrieved 2012-02-24.
- p.233 of On the Philosophy of Discovery: Chapters Historical and Critical (Including completion of the third edition of the philosophy of the inductive sciences), William Whewell, New York: Burt Franklin, 1860
- H. Floris Cohen, The Scientific Revolution: A Historiographical Inquiry, University of Chicago Press 1994, p.35-39
- Notebook N (Metaphysics and Expression). Charles Darwin. Journal's timespan: fall 1838—summer 1839. page[leaf] 12.