Rene Descartes is widely regarded as the father of rationalism, a philosophical approach that emphasizes the role of reason and intellect in understanding the world.

Descartes proposed that the fundamental substance of the universe is mind, or thinking substance, rather than matter.

Descartes' famous statement, 'Cogito ergo sum' ('I think, therefore I am'), encapsulates his belief that the existence of the self can be established through the act of thinking.

Rationalists like Descartes argued for dualism, the view that the mind and body are two distinct and separate substances.

Gottfried Leibniz, a prominent rationalist, proposed the concept of 'innate ideas,' which are ideas that are present in the mind from birth.

Rationalists emphasize the role of reason and intellect as the primary source of knowledge, rather than relying solely on sense experience.

Thomas Aquinas, a prominent rationalist, argued for the existence of God through rational arguments, known as the Five Ways.

Rationalists hold that the mind is capable of grasping universal and necessary truths that are not derived from sense experience, a view known as apriorism.

Rene Descartes introduced the concept of 'clear and distinct ideas,' which are ideas that are free from doubt and ambiguity.

Rationalists view sense experience as secondary to reason and intellect in the process of acquiring knowledge.

John Locke, an empiricist rather than a rationalist, argued that the mind is a blank slate at birth and all knowledge is derived from experience.

Rationalists hold that the mind is capable of grasping abstract and universal concepts, a view known as conceptualism.

Gottfried Leibniz introduced the concept of 'monads,' which are simple, indivisible substances that make up the universe.

Rationalists typically argue that the mind and the body are distinct and separate substances, a view known as dualism.

Gottfried Leibniz proposed the concept of 'the harmony of pre-established harmony,' which suggests that the mind and the body operate in harmony without direct causal interaction.