Philosophical theory in the context of "Practical philosophy"

The Theory of Forms or Theory of Ideas, also known as Platonic idealism or Platonic realism, is a philosophical theory credited to the Classical Greek philosopher Plato.

A major concept in metaphysics, the theory suggests that the physical world is not as real or true as Forms. According to this theory, Forms—conventionally capitalized and also commonly translated as Ideas—are the timeless, absolute, non-physical, and unchangeable essences of all things, which objects and matter in the physical world merely participate in, imitate, or resemble. In other words, Forms are various abstract ideals that exist even outside of human minds and that constitute the basis of reality. Thus, Plato's Theory of Forms is a type of philosophical realism, asserting that certain ideas are literally real, and a type of idealism, asserting that reality is fundamentally composed of ideas, or abstract objects.

The modern division of philosophy into theoretical philosophy and practical philosophy has its origin in Aristotle's categories of natural philosophy and moral philosophy. The one has theory for its object, and the other practice.

Dogma, in its broadest sense, is any belief held definitively and without the possibility of reform. It may be in the form of an official system of principles or doctrines of a religion, such as Judaism, Roman Catholicism, Protestantism, or Islam, the positions of a philosopher or philosophical school, such as Stoicism, and political belief systems such as fascism, socialism, progressivism, liberalism, and conservatism.

In the pejorative sense, dogma refers to enforced decisions, such as those of aggressive political interests or authorities. More generally, it is applied to some strong belief that its adherents are not willing to discuss rationally. This attitude is named as a dogmatic one, or dogmatism, and is often used to refer to matters related to religion, though this pejorative sense strays far from the formal sense in which it is applied to religious belief. The pejorative sense is not limited to theistic attitudes alone and is often used with respect to political or philosophical dogmas.

George Berkeley (/ˈbɑːrkli/ BARK-lee; 12 March 1685 – 14 January 1753), known as Bishop Berkeley (Bishop of Cloyne of the Anglican Church of Ireland), was an Anglo-Irish philosopher, writer, and clergyman who is regarded as the founder of "immaterialism", a philosophical theory he developed which later came to be known as subjective idealism. He has also been called "the father of idealism" by German philosopher Arthur Schopenhauer. Berkeley played a leading role in the empiricism movement and was one of its pioneers. He was among the most cited philosophers of 18th-century Europe, and his works deeply influenced later thinkers such as Immanuel Kant and David Hume.

In 1709, Berkeley published his first major work An Essay Towards a New Theory of Vision, in which he discussed the limitations of human vision and advanced the theory that the proper objects of sight are not material objects, but light and colour. This foreshadowed his most well-known philosophical work A Treatise Concerning the Principles of Human Knowledge, published in 1710, which, after its poor reception, he rewrote in dialogue form and published under the title Three Dialogues Between Hylas and Philonous in 1713. In this book, Berkeley's views were represented by Philonous (Greek: "lover of mind"), while Hylas ("hyle", Greek: "matter") embodies Berkeley's opponents, in particular John Locke.