The Principle of Causality
The law of causality, al-Sadr states, is a necessary rational principle present in the core of man's nature as a rational being. It is on the basis of this principle that (1) the objective reality of sense perception, (2) the validity of scientific theories and laws based on experimentation and (3) the validity of all philosophical and scientific inference, are based.
Al-Sadr explains that although the objective existence of the world is a necessary primary judgement that requires no evidence, the objective reality of every particular sense perception is not known in a necessary manner. It is on the basis of the principle of causality that a specific perception, under specific circumstances and conditions, reveals the existence of its cause as an external object.
Experimental theories do not acquire a scientific character unless they are generalized beyond the limits of particular experiments. And this is not possible without reliance on general causal laws which are: (1) the principle that every event has a cause, (2) the principle that every cause necessarily produces its effect, and (3) the principle of harmony between causes and effects.
Without the laws of causality, there would not be any link between evidence and conclusions and no evidence would lead to any result.
Even those who attempt to deny this principle by resorting to a certain evidence would not make this attempt had they not believed that the evidence on which they rely is a sufficient cause of the knowledge of the falsity of this principle. But this is in itself an application of this principle.
It is wrong to regard the principle of causality as an inductive law based on experimentation, because such a view reopens the fundamental question about the validity of perception and experimentation, to which no answer can be found. It is a principle which is accepted independently of the senses and is above experimentation. From the viewpoint of Islamic philosophers, (1) causality is not limited to the natural phenomena which figure in experimentation, but is a general law of existence, applicable to the material and the immaterial; (2) the cause whose existence is confirmed by this principle need not be subject to experimentation, nor it need be of a material nature; (3) the fact that experimentation does not disclose a specific cause of a certain phenomenon does not imply a failure on the part of this principle, for it does not rest on experimentation. These salient points differentiate the mechanistic, materialistic interpretation of the law of causality from its theological interpretation. Causality and Microphysics:
Inevitable uncertainty entered the realm of modern physics as a result of experimentation with subatomic particles. If the position of an electron were to be accurately measured, radiations of very small wavelength would have to be used for the determination. But such radiations possess quanta of high energy, and would alter the momentum and energy of the electron by impact. Similarly, to measure the momentum of an electron, quanta of low energy would have to be used.
The wavelengths of such quanta being large, the position of the electron would be correspondingly indeterminate. Heisenberg's Principle of Uncertainty followed from the wave-particle duality of matter and radiation, and from the fact that the characteristics of objects were usually unavoidably altered during the course of experimentation.
The indeterminacy at the subatomic level meant that there could be only probabilistic knowledge of subatomic events. This fact made the physicists and erroneously according to al-Sadr abandon belief in the universality of the principle of causality. Not only that, they came to interpret the causal fixity and regularity of macroscopic events as a statistical phenomenon, analogous to the stability of, say, suicide rates.
Al-Sadr points out that the doubts raised by scientists in microphysics are based on a specific notion of the principle of causality different from the notion of it held by Muslim philosophers. According to the latter notion, the principle is not based on experimental evidence and stands above experimentation. Moreover, the limits of experiment prove only our inability to apply it in some fields, not the invalidity of this principle in those fields. In addition, microphysical experiments do not offer any scientific evidence proving the falsity of the principle of causality in the field of subatomic physics. The introduction of indeterminacy is a problem of the observing subject, something which does not warrant the elimination of causal laws from the universe.