What is Rationalism? - Definition & Philosophy

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  • 0:04 Rationalism Definition
  • 1:09 Acquiring Knowledge
  • 2:16 Metaphysical & Ethical Truths
  • 3:01 Rationalist Philosophy
  • 4:34 Lesson Summary
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Lesson Transcript
Instructor: Joe Ricker
Rationalism is a fairly straight-forward way of thinking that promotes the belief that knowledge can be gained outside of experience. In fact, rationalism essentially functions with the notion that experience isn't necessary to acquire knowledge.

Rationalism Definition

Most of us have heard the expression, ''Be rational'', especially when we're reacting emotionally. This is like when our motivations are inspired by things that don't necessarily make a lot of sense to other people, or it's clear that our perspective is skewed because of our feelings. Like our feelings, our senses can also project a skewed perception of reality. Take optical illusions for example. Our sense of truth isn't actually real, so we're not being rational.

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.
  2. Innate Ideas, which are the ideas that we're born with, and in some ways, shape our personality.
  3. Reason, which means using logic to arrive at a conclusion.

While deduction relies on principles or formulas to find answers, reason offers different ways to find the truth or draw conclusions. For example, let's take the biblical story of the Judgment of Solomon. Solomon had to resolve a dispute between two women who claimed to be the mother of a baby. Since this was long before DNA testing, Solomon ordered that the baby be cut in half.

Upon hearing this, one of the women cried out not to harm the child and to let the other woman take the baby. Solomon concluded through logic that the woman who cried out to spare the child was actually the child's mother because the mother would rather the child live than win an argument.

Metaphysical & Ethical Truths

Rationalism finds that truths are held by intellect. As rationalism became a more popular philosophy in the 17th and 18th centuries, it was also connected to metaphysical truths and ethical truths. For example, the statement: ''Slavery is wrong'' is an example of an ethical truth, which makes it a rational belief.

Rationalist thinkers believe that knowledge, or our understanding of truth, is acquired without sense perception. In other words, knowledge is acquired through a secular outlook, which is an outlook that is absent of religious influence. This doesn't mean that rational thinkers were atheists, though some were. Most early rationalists believed that our innate ideas were given to us from God.

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