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Lesson · 4 min Steady

Essence and Existence

In one line A description tells you what a thing is, not that it exists.

Ibn Sina separates two questions that like to borrow each other’s clothes. What a thing is, and that it is. You can describe a house down to the hinge and still be standing in an empty field.

For the things we meet, existence is not packed inside the description. A perfect account of a medicine does not put a bottle on the shelf. The what can be finished while the that is still missing.

Keep a second question handy. When an argument hands you a vivid description, ask whether anything answering to it has been found. A definition can be exact and still describe nothing in the world.

Go deeper

Ibn Sina argued that the essence of a thing, what it is, does not include its existence, since you can know what a triangle is without knowing whether one exists. So for every ordinary thing, existence is added by a cause.

He used this to argue that there must be one being whose essence is existence, which he took to be God; later thinkers, including Aquinas, took up and reshaped the idea.

The house on the paper

Illustration: The house on the paper

A page draws a clinic: the rooms, the hours, the illness it would treat. The drawing is careful. There is no building, no key, no patient.

Ibn Sina would say you have the essence. You do not yet have the existence. Wanting the clinic, and describing it, are not the same as finding it.

Try this today When an idea sounds persuasive, ask whether anyone has actually found the thing it describes.

Question 1 of 2

A page describes a medicine in full: what it is, what it would treat, and how it would work. No batch has been made, and no patient has taken it.

What do you have, and what is still missing?

Question 2 of 2

A cousin says a careful definition is enough to settle that the thing is real.

What does Ibn Sina refuse here?

Cite or share this lesson

A plain reference you can paste into notes or an essay:

Quest2Reason. “Essence and Existence.” https://quest2reason.com/learn/lesson/essence-existence. Accessed 13 November 2026.

Sources
  • Stanford Encyclopedia of Philosophy, “Ibn Sina (Avicenna)” — Covers his distinction between essence and existence.
  • Ibn Sina, The Cure (Kitab al-Shifa), Metaphysics — Essence, what a thing is, is distinct from existence, that it is, in everything that might or might not be.
  • Ibn Sina, Remarks and Admonitions (al-Isharat) — A thing’s description does not include the news that one exists, except for the one necessary being he argues for separately.
  • Wikipedia, “Essence” — What a thing is, as distinct from whether it is.