Avicenna and Averroes played an important role as a key between humanism, French and English materialism, and the Greek thought that was developed during antiquity.
The reason for that is that materialism as conceived by the Greek thinkers did not integrate the concept of movement. Democritus' atomism was materialistic, but did not explain the movement of atoms (which were also, in a anti-dialectic way, considered as “unbreakable”, the Greek atomos meaning « indivisible »).
Democritus did not explain why atoms were forming forms and not others, and how and why these forms were moving. That's why Aristotle could so easily develop his conception and have such a great success.
His basic conception – the principle of cause and consequence – was idealistic (see our articles Engels on cause and effect and "An effect can not occur before the cause which is its origin" [dialectical materialism rejects the concepts of "cause" and "consequence") – not translated in English). But they could help to build a general theory of matter and movement.
The problem of the old Greek materialism is that the universe was static, it has no movement, reality could not be observed and studied, because matter was all but had no movement, no sense itself.
Whereas with Aristotelianism, universe is moving, even if only in circles, in a repetitive manner. So, it is possible to understand this.
Avicenna and Averroes went further than that. They push Aristotle's logic to a peak. As there was a primary cause to everything, then logically randomness became an impossibility. The door was open to understand the world as a whole system.
A repetitive system, indeed. Until Spinoza, materialism was not able to conceive the sens of evolutionary movement. Hegel played a central role in giving the possibility to understand qualitative leap, evolutionary movement or better said : revolutionary movement.
Nevertheless, Avicenna and Averroes were key figures of the construction of the “system” permitting to understand the world. As the Islamic religion was affirming that there was a “God” source of everything, then the “first motor” described by Aristotle must have been this unique God.
And so, the universe was a rational system. There was no room for randomness. The reason for that was that to the cause as source of movement – the efficient cause, the material cause – another concept was added: the concept of “final cause”.
Aristotelianism won over Democritus' materialism because Democritus could not see a cause in the movement of matter. Aristotle did not understand the nature of matter, but he recognized that matter was moving in a specific direction.
So, there was a “final cause”. Even if there were some rare events where obstacles were impeaching a natural movement, what is preponderant is the final cause.
We may not understand what appears as random, but it is not random. It is just something more complicated. It was Avicenna that introduce the principle of a “normal” situation as an “uninterrupted sequence” (ittirad).
So, what was “rare” was only a sequence that was interrupted: “Indeed the rare turns out to be necessary (wajib) if the conditions in it are established and the circumstances are expressed.” (Tafsir k. al-Sama' al- tabi'i, commentaire sur la Physique d'Aristote)
Avicenna's thought reaches here an important materialist level, but also its limit. Indeed, what can interrupt the sequence?
Because of the idealist nature of the cause-consequence system, Avicenna can only blame nature itself. Nature is not “pure” as the content given to it by God. So, there are troubles in the combination of matter, interrupting sequences.
Here is what Avicenna says:
“It is clear from all this that the natural movements of the material elements are by way of a natural aim (qasd) from them to a definite place (hadd mahdud), and that that happens always or for the most part, and this is what we mean by the terme “end” (ghaya).
Then it is obvious that the goals that emanate from nature when nature is not opposed [to that], and does not place obstacles, are good and perfect.
If they lead to a bad end that is not always or for the most part, rather in a way such that our soul looks for an accidental cause in these things, and it is said “what made these palm shoots wither?”, and “what made this woman miscarry?”
Even if this happens, nature moves for the sake of good, and this is not only [observable] in animal and vegetable growth, but also in the movement of simple bodies and in the actions which emanate from them by nature (bi-l-tab'). For they always move towards ends, provided that nothing impedes them, according to a definite order (nizam mahdud) without deviation, unless there is an opposing cause.” (Tafsir k. al-Sama' al- tabi'i, Commentary on the Physics)
There is a final cause, but its sequence may be interrupted. There are reasons for that, because everything has a cause. Interrupted things are not correct, but they do exist, because of the nature of matter.
Here is what Averroes says, giving an example to it:
“Amongst the things which are for an end, some rarely happen. However, from them results something other than that end, such as encountering one's debtor in the marketplace.
This happens rarely, but happens as a consequence of walking to the marketplace, which was for some other purpose... Chance and the spontaneous exist in things/events, which are in a minority of cases, and come from things, which are for the sake of some cause, but they failed [to attain] that [final] cause, and another [final] cause [or end] came to be from them.” (Long Commentary on the Physics)
What we see here is the logical understanding of the cause-consequence system. This system permits to understand the world, as long as the cause brings the consequence. But if there are some troubles, then it is because some things with cause perturb the logical cause-consequence movement of others things.
In fact, more than something else, the problem for this is that Avicenna and Averroes admitted Aristotle's concept of movement as an eternal circle. There are no place for perturbations, trouble... a qualitative leap. This is the criticism made to Spinoza by Hegel.
The system of Aristotle, Avicenna, Averroes is based on individual forms with cause and going to an end. Individual forms obey to a plan that comes from outside the matter. Nevertheless, because of the nature of matter, the plan can not be realized all the times because of special causes, where different causes come bumping into each other.
Because of the potentiality in matter – the possibility of cause – there is chaos. There is a shift between the original purpose and what happens. This is the basic problem of the cause-consequence logic, a logic explained here by Averroes commenting Aristotle:
“Nature is said according to matter and form... The form is the end in generation, and everything that is before the end is for an end/purpose.
Therefore it is necessary that everything that is before the form should be for the sake of the form...
Also, it is necessary that the form should be the end in generation, because form follows from the agent, either always, or for the most part, and consequently matter is for the sake of form.” (Long Commentary on the Physics)