Rationalism, in Western philosophy, the view that regards reason as the chief source and test of

knowledge. Holding that reality itself has an inherently logical structure, the rationalist asserts that a
class of truths exists that the intellect can grasp directly.

(Rationalism is an epistemological position in which reason is said to be the primary source of all
knowledge, superior to the senses.

In general, rationalists believe that abstract reasoning can produce undeniable, absolutely certain truths
about nature, existence, and the whole of reality.)

PHILOSOPHY

The theory that reason rather than experience is the foundation of certainty in knowledge.

(Rationalism has long been the rival of empiricism, the doctrine that all knowledge comes from, and
must be tested by, sense experience. As against this doctrine, rationalism holds reason to be a faculty
that can lay hold of truths beyond the reach of sense perception, both in certainty and generality.

Essentially, rationalism regards reason as the chief source and test of knowledge or what’s true. Truth, in
the case of rationalism, is not sensory but intellectual, which is why rationalists believe that knowledge
can be acquired through reason alone.

This makes rationalism a priori, meaning that we gain knowledge without experience through the use of
reason. Rationalism applies primarily to logic and mathematics, meaning that there is a calculated and
reasoned approach to conclusions or the truth.

Acquiring Knowledge

In rationalism, knowledge is acquired in three ways:

1. Deduction, which means applying principles to draw conclusions. For example, finding the area
of a rectangle. For any rectangle, the same principle is applied to find the area.

- What is deductive reasoning?

-In a simple deductive logic argument, you’ll often begin with a premise, and add another
premise. Then, you form a conclusion based on these two premises. This format is called
“premise-premise conclusion.”
Examples: Deductive logic arguments

Premise: All insects have exactly six legs.

Premise: Spiders have eight legs.

Conclusion: Therefore, spiders are not insects.

- What is an innate thought?

In philosophy and psychology, an innate idea is knowledge or a concept that is considered universal to
all humanity; it is something people are born with rather than something learned through experience.

EXAMPLE: debate ni DECARTES and John Locke

3. Reason, which means using logic to arrive at a conclusion.

History of Rationalism

The term “rationalist” came into being in the 1620s. Rationalists were identified as people who did not
follow authority, but reason, in their lives and decision making. But it is thought that the first
proponents of the rationalist school of thought lived and worked between the 6 th and 4th centuries BCE,
in Ancient Greece and China . The Ancient Greek philosophers Pythagoras, Parmenides, Plato, and
Aristotle, and the Chinese philosophers Confucius and Lao-tzu (the latter being the attributed founder of
Daoism), laid the groundwork for contemporary philosophies of rationalism. Each of these practitioners
believed that there is an order to all things, and that there is a fundamental knowledge base informing
everyday life.

Rationalism, as it is known today in the West, began to take shape under the work of St. Thomas
Aquinas in the 12th century. It then came to the fore during the Enlightenment period, between the 16 th
and 18th centuries. Thinkers Descartes, Spinoza, and Leibniz elaborated on the basic concepts of
rationalism as a framework of fundamental understandings, resulting in seminal theories that are still in
play today.

René Descartes is generally considered the father of modern philosophy.

Descartes constructed his cogito ergo sum, ‘I think, therefore I am,’ during his studies of rationalism. He
believed that there was an ultimate truth that a person might pursue understanding of, if they were
willing to first doubt everything. He grounded his work in a priori thought, or the theory that all human
beings carry a base of knowledge that is not dependent on life experience.
  René Descartes (1596-1650)
 René Descartes is generally considered the father of modern philosophy. He was the first major
figure in the philosophical movement known as rationalism, a method of understanding the
world based on the use of reason as the means to attain knowledge..
 Descartes constructed his cogito ergo sum, ‘I think, therefore I am,’ during his studies of
rationalism. He believed that there was an ultimate truth that a person might pursue
understanding of, if they were willing to first doubt everything.
 I think therefore I am. (philosophy) I am able to think, therefore I exist. A philosophical proof of
existence based on the fact that someone capable of any form of thought necessarily exists.
 He grounded his work in a priori thought, or the theory that all human beings carry a base of
knowledge that is not dependent on life experience.
 Father of modern rationalism.
 Reason is the source of knowledge, not experience.
 All our ideas are innate.
 God fashioned us with these ideas.
 • We discover basic truths by intuition: by grasping basic connections between the ideas we
have.
 We deduce or demonstrate more complex truths.

Along with empiricism, which stresses the use of sense perception rather than pure reason, rationalism
was one of the main intellectual currents of the Enlightenment, a cultural movement spanning the
seventeenth and eighteenth centuries that revolutionized the Western world. In tandem with men like
John Locke, John Hobbes, and Voltaire. Descartes spurred society to re examine its traditions and
institutions, leading to massive social upheaval Both the American and French Revolutions were based
on Enlightenment theories, and the ways we approach science, math, philosophy, and the idea of the
self were radically transformed during the period.

Spinoza was more preoccupied with the existence of the universe than the existence of the self, as
Descartes had been. Leibniz, meanwhile, proposed that all truths are true, but that humans are not
necessarily able to understand and perceive those truths (a famous line from him being “snow is white;
snow must be white.”)