Faith and Reason: Avicenna and Al-Ghazali

Avicenna (980-1037 AD)

Polymath and prodigy. Memorized the Quran at 10.

Learned Indian arithmetic, Greek Geometry, and studied Aristotle before turning to medicine at 16.

By 18, a respected physician. Innovator in modal logic, physics. 450 written works.

Al-Ghazali (1058-1111 AD)

Born into poverty in Tus, Iran (Persia).

On the basis of his legal and theological work, rises to prominence in the Nizamiyya school as "Brilliance of the Religion".

Abandons career for life as an ascetic and mystic.


Mu'tazilite and Falsafa: two schools of philosophy

Mu'tazilites: Rationalistic theology (Kalam). Reason is the arbiter of morality. Theory of scriptural interpretation.

Falsafa: Influenced by greek philosophy. World is eternal, not created (as a consequence of God's perfection). Existence and nature of God and the Soul can be established by reason. (Avicenna)

Falsafa: God, and the Soul.

Avicenna's Falling Man

One of us (i.e. a human being) should be imagined as having been created in a single stroke; created perfect and complete but with his vision obscured so that he cannot perceive external entities; created falling through air or a void, in such a manner that he is not struck by the firmness of the air in any way that compels him to feel it, and with his limbs separated so that they do not come in contact with or touch each other.

Then contemplate the following: can he be assured of the existence of himself? He does not have any doubt in that his self exists, without thereby asserting that he has any exterior limbs, nor any internal organs, neither heart nor brain, nor any one of the exterior things at all; but rather he can affirm the existence of himself, without thereby asserting there that this self has any extension in space.

... Therefore the self, the existence of which has been asserted, is a unique characteristic, in as much that it is not as such the same as the body or the limbs, which have not been ascertained. Thus that which is ascertained (i.e. the self), does have a way of being sure of the existence of the soul as something other than the body, even something non-bodily; this he knows, this he should understand intuitively, if it is that he is ignorant off it and needs to be beaten with a stick

Cosmological Argument

(Heavy Reconstruction)

  1. There are some contingent things.
  2. All contingent things require causes.
  3. A totality of contingent things is contingent

Therefore, there is a necessary cause.

For Principle 3

If they are existent together and there is nothing necessary of existence among them, then inevitably their total, insofar as it is that total, whether it is finite or infinite, is either necessary of existence by itself or possible of existence. So if it is necessary of existence by itself, but each of its units is possible, the necessary of existence would be composed of possibles of existence, which is absurd. And if it is possible of existence by itself, the total needs for existence something to bestow existence


Against causation:

The connection between what is customarily regarded as a cause and what is believed to be an effect is not necessary, according to our opinion... On the contrary, it is within the power of God to create satisfying hunger without eating, ... to allow life to continue even if decapitation occurs, and so forth for all connections. The falsafa, however, deny this.

What of the proof of the observation that fire is the acting cause? He has no proof except that burning occurs when there is contact with fire. However, observation only proves that one occurs together with the other, but it does not prove that one occurs though the agency of the other

[if a blind man is made to see] and he sees colors, he will think the opening of his sight is the acting cause of the perception of the forms of colors... he will not understand that he cannot see [after] the sun sets and the air is dark. On what evidence does our opponent believe that there exist causes... unless it is that events are constant?

A possible reply

The opponent could reply: this opinion leads to the perpetuation of abominable impossibilities. If you deny the necessary connection between effects and causes and attribute the effects to the will of their creator, and maintain that the will does not have a well-defined pattern... each one of us would have to consider it possible that there might be him his presence wild beasts, raging fires...

In answer to this argument, we say: if it could be shown that the existence of the possible implies that knowledge of its non-existence cannot be created, these absurdities will necessarily follow... [by the grace of God], if something happens time after time, its habitual course will be firmly rooted in our minds...

Reconceptualizing possibility

Impossibility arises only from logical relationships between terms.

The impossible is the simultaneous affirmation and denial of something...If the denial of whiteness is understood from the affirmation of blackness, then the simultaneous affirmation of denial of of whiteness is impossible.