The hole in Avicennan Metaphysics.
According to Aristotle, a proposition always contains a subject and its accidents. Of a triangle, its substance or essence is its three angles. Its accidents may be the colour or specific ratios of the angles, these are not essential to the being of a triangle, for we do not recognize a triangle by them.
A triangle as has so called “per-se accidents”. A per-se accident of a triangle is that the sum of all angles always equals the sum of two right angles (180° or πrad). This is an accident because we do not recognize a triangle by its adherence to this principle. Yet it does show what a triangle as-such is. Therefore, it is a per-se accident.
Avicenna takes “existence” to be such a per-se accident. In other words, it is not in the essence of a thing that it exists, this is “merely” an accident. This leaves Avicenna’s metaphysics with a hole, one Avicenna was eager to fill with theology. The essence of God, Avicenna claims, is such that He must necessarily exist. He is the essential- or necessary-being.
A similar hole exists at the bottom of physics, namely the theory of the Big Bang. The Big Bang Theory starts that in the early moments of our universe, all matter was condensed in a point of near-infinite density at high temperature. The universe as we know it started as a mass-expansion from this incredibly dense point. While the theory has many interesting notes, there is one I wish to call attention to that being the claims made about what occurred before the Big Bang. The Big Bang denotes the moment in history where our physical models and theories break down. It is the wall which we cannot look beyond. In other words, there are no (scientific) claims made about what came before- or what caused-the Big Bang.
This gap in physics of course leaves the floor open for theologians and other intellectuals to hypothesize about the state of our pre-infant-universe. Not much unlike Avicenna’s gap in metaphysics. The reason I brought the gap in physics into a discussion about medieval philosophy is to call attention to an important distinction one has to make: Avicenna left a gap, that does not mean he did so intentionally to make room for his theology. I think that to take Avicenna as a malicious manufacturer of holes would be the least charitable interpretation possible. Rather, I would say that Avicenna’s metaphysical theories were attempts to explain the word to the best of the master’s abilities. Subsequently, the filling of the gap using theology was hist best attempt at making his theories coherent and complete. Much like the scientists of modern day accepted the limits of the current models giving the point where they break down a name: The Big Bang, and continuing by explaining as much as possible about it.