In one sense first member of a causal series is a part of the series, but in another sense it isn’t. If ABCD causes something, then A is obviously 1/4 of all the causes you have, but we don’t think about it that way. We don’t say that George Bush played a part in the Iraq War, or even a crucial part in it – it was just his war. Truman wasn’t a part of the system that dropped the bomb – the system was brought int existence by his choice. This is true in every genus of causes. Winning isn’t one part of an athlete’s goals, even if one can isolate other goals than this in the game or in training. A fire hydrant is red and a light wave in the right spectrum is red, but the “is” is not said in the same way. The two things “are red” but not in a way that the one is a part of the whole.
James’ blog on Thomism is one of the best philosophy blogs on the internet. I really appreciate his succinct explanations of complicated topics. In this case he hits the nail on the head. Many Christians accidentally see God as a figure within the cosmos. This is right and good as far as such images support Christian piety because the are the models utilized in Scripture. But insofar as they are mistaken for giving precise expression concerning God’s reality, such ideas (God is a part of the furniture of the universe) tend toward treating God as a creature. The Bible, in its more literal moments, treats God as the being in whom all things live and move and have their being. Similarly, God is the cause of all non-God reality in Genesis 1, John 1, and Hebrews 1. I’ve written elsewhere about how open theism and forms of Calvinism both take anthropomorphic language about God (preordaining and being surprised) too literally.