In practice in it does not matter too much where you begin in Thomistic philosophy. The reason for this is that true philosophy is essentially organic. You begin at one part of the body and if you keep going you will eventually cover everything. The diverse parts are all related. Why is this so? Because philosophy is a speculum, a mirror of reality. Just as reality is consistent with itself, being a logical order of things, so does a realist philosophy enjoy the same kind of cosmological harmony. The universe is the cosmos, the ordered, and philosophy reflects this, even taking into account the disorder caused by sin.
This organic unity is only analogously compared with the unity of a body, which can be perceived in a way even by the senses. The unity of philosophy is not merely a material unity, of one thing touching another. Philosophy enjoys a unity of reason. Why does one thing lead to another in philosophy? Because reason compels us to take that next step.
Let us enter at the treatise on Sensitive Psychology. We consider the nature of sense knowledge. In adverting to the fact that we have this knowledge in common with the brute animals, we are aware that human knowledge must contain another intellectual dimension to make considering knowledge at all possible. We thus enter the domain of Intellective Psychology. But even while we were in Sensitive Psychology there were many connections we could make: between the different senses, the sense appetites and passions, considering concepts such as knowledge and love, with profound implications in Intellective Psychology, and principles such as, "Every knowledge is followed by a proportionate inclination".
Within Intellective Psychology we are confronted with many issues which take us straight to other philosophical sciences. The topic on the Will takes us to the science of Ethics. This in turn leads to consideration of the pure, infinite Good, which gives our existence meaning. Consideration of the adequate object of the human intellect takes us to Metaphysics and Logic. Epistemology defends our ability to know being. Ontology, with its study of being and analogy tells us how far the human intellect can go in knowledge. Logic shows us how to use our reason well in order to attain correct conclusions from right premises. Having ascertained the spirituality of the human soul, we are taken on the wings of Natural Theology to contemplate the wonders of the divine intellect, in whose knowledge the human intellect participates. In the topic on obediential potency we even venture into the domain of Sacred Theology – this last journey of course requiring Divine Revelation as the starting point. Such organic unity is found in an even deeper way in Sacred Theology since the realities considered are supernatural and have their intrinsic connection in the Economy of Salvation willed by God.
Andrew Nimmo is a lecturer at the Centre for Thomistic Studies, in Sydney, Australia.
This article posted May 2000. It was published in Universitas, Vol 2 (1998), No. 2.
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