In this work, I argue that there is a non-trivial historical-theoretical context in which a sound, deductive argument for the immateriality of the human intellect can be given entirely based on Thomas Aquinas’s philosophical framework. Aquinas presents several arguments for the immateriality of the human intellect. His preferred arguments for this conclusion are sometimes known as the two universality arguments, because they are based on the universal aspects of human intellectual cognition. According to the argument from the universal scope of intellectual cognition, the intellect must be immaterial because it is capable of knowing the natures or essences of all material substances, which nothing material could do. According to the argument from the universal mode of human intellectual cognition, the intellect must be immaterial because nothing material could cognize its objects in the abstract, universal mode of the intellect.
These two arguments have recently received critical scholarly attention. The scope argument is considered unsuccessful by nearly all of Aquinas’s recent commentators, whereas the mode argument has been frequently defended in the literature. However, the mode argument has also been criticized for an allegedly unjustified inference known as the “content fallacy”: just because something represents universally and thus immaterially, it does not follow that it is ontologically immaterial itself, unless further argumentation is provided.
Several replies have been given to the “content fallacy” objection, but these leave the matter inconclusive at best in my opinion. I think the content fallacy can be overcome, but this requires taking into consideration Aquinas’s views on how the intellect actively causes or abstracts the cognitive representations of the essences it cognizes. The resulting argument, which I call the causal universality argument, is nowhere found in Aquinas’s works in a dialectically satisfying form. However, it is an argument entirely based on Aquinas’s theoretical framework. Thus, even if it is an argument Aquinas never intended to make, it is an argument he could have coherently given without adding anything new to his philosophy.
Demonstrating the immateriality of the human intellect is important to Aquinas for several reasons. For example, it is a part of Aquinas’s larger project of trying to philosophically establish the incorruptibility and immortality of the human soul, which makes the resurrection of the human being at least a coherent possibility from a philosophical point of view. If the causal universality argument is sound relative to its proper theoretical context as I argue, then Aquinas has a good basis on which to argue for these further claims.
