A thesis refers to the main argument, point, purpose, or theme of a piece of writing and is often referred to as a thesis statement, which is a proposition to be argued.
The concept of thesis, antithesis, and synthesis specifically refers to the work of German philosopher Friedrich Hegel. The thesis presents a proposition; the antithesis is the opposite of the thesis, a reaction to the proposition; and the synthesis resolves the conflict between the two by recognizing their common properties and forming a new proposition. This represents a particular logical process in philosophy that has been translated into more general usage for developing claims in many fields.