Gottfried Leibniz's Principle of Sufficient Reason

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  • 0:01 Principle of Sufficient Reason
  • 1:13 Self-Contained vs. External
  • 2:26 Cosmological Argument
  • 3:19 Questions & Critiques
  • 4:15 Lesson Summary
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Lesson Transcript
Instructor: Jessica Whittemore

Jessica has taught junior high history and college seminar courses. She has a master's degree in education.

This lesson will explain the principle of sufficient reason. In doing this, it will highlight the assertions of Gottfried Leibniz and the cosmological argument for the existence of God.

Principle of Sufficient Reason

Every child's nightmare is the sentence, 'Why did you do that?' Really, I hated it. I'd accidentally break a glass, my mom would say, 'Why'd you do that?' I'd stay out too late, my dad would bark, 'Why'd you do that?'

Of course, I could never come up with a reason, and this seemed to make them even angrier. Although this seemed like nonsense to me, my parents were, without knowing it, giving me a crash course on the principle of sufficient reason espoused by Gottfried Leibniz. Today, we'll take a look at this principle.

Let's start with a definition. The principle of sufficient reason holds that for every state of affairs or true proposition, there is an explanation of why it is the way it is. Stated for those of us who aren't philosophers, everything has a reason. Although my parents seemed to have the market cornered on this one, the principle of sufficient reason is usually linked to Gottfried Leibniz, a 17th century philosopher who used it to support the existence of God. However, before we get to the God part, let's take a closer look at the principle.

Self-Contained vs. External

First, the principle of sufficient reason holds that there are two types of reasons or causes, self-contained and external. Self-contained explanations pertain to things like math and abstract objects. They are things that ARE simply because they ARE. For instance, a triangle is a triangle simply because it's a triangle. What it is actually contains the explanation for why it is.

On the contrary, external explanations pertain to things like events, objects, and creatures. External reasons are forces outside an event that cause the event. For example, volcanoes erupt and flowers bloom for external reasons.

To loop back, my parents wanted an external explanation for why I was late. Was it because I was misbehaving? Was it because I was in an accident? Was it because I just decided to blow off my curfew? Although none of these reasons would have made them happy, the idea of trying to give them a self-contained explanation, 'I'm late simply because my essence is late', would've really ticked them off!

Like Gottfried Leibniz, they held to the principle of sufficient reason - events, creatures, and objects have an external explanation.

Cosmological Argument

Leaving my teenage years in the past, let's take a look at how our principle pertains to God. For this, we turn to the cosmological argument, an assertion that seeks to prove the existence of God.

Now, according to the principle of sufficient reason, everything must have a reason for its being. If the thing is mathematically related (i.e., a triangle is a triangle), it's okay if this reason is self-contained. However, if the thing is an event, object, or creature, its reason for existing has to be external. In other words, something else had to act upon it to bring it into being.

Now, since the universe is an object, our principle asserts that some sort of external something has to be the reason for its existence. Enter the cosmological argument for God, the idea that God is the first reason or first cause of the universe.

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