When modern science approaches the world, it asks two questions of it: what is the nature and arrangement of the matter under consideration, and how did that arrangement come to be? If one is a methodological naturalist, then the only valid answers to the second question are physical.
In Aristotelian terms, modern science is interested in two causes: the material (what is it made of?) and the efficient (how was it made?). The formal cause--what is it?--and the final cause--what is its purpose?--have no bearing on scientific inquiry.
In the epilogue to his extraordinary The Discarded Image, C.S. Lewis points out, "But nature gives most of her evidence in answer to the questions we ask her. Here, as in the courts, the character of the evidence depends on the shape of the examination, and a good cross-examiner can do wonders. He will not elicit falsehoods from an honest witness. But, in relation to the total truth in the witness's mind, the structure of the examination is like a stencil. It determines how much of that total truth will appear and what pattern it will suggest."
In other words, asking some questions of nature and not others will inevitably lead to an incomplete--and in that respect, inaccurate--model. What this means, however, is that the notion that we can understand the material composition of a thing abstracted from its form or purpose is questionable. We will certainly learn a lot about the material composition--we may even be able to manipulate that object in interesting and "productive" ways. But we will not understand that which we are manipulating. The formal and final causes--the "what is it" and "what is it for"--relate to the material and efficient causes. To see them as isolated divides reality from itself, giving us a stunted impression of both the material and efficient causes on the one hand, and the formal and final causes on the other. (This may be the difference between modern and medieval science: the medievals wanted understanding, leaving the control to the magicians, whereas moderns more often allow the desire for control to motivate their scientific endeavors).*
For this reason, the relationship between science and theology must be maintained. Each impinges upon the other--if we wish to understand the physical reality of creation, then we must understand it as creation. If we wish to understand the mind of God, we must study the text(s) He has written. Ultimately, reality is unified and so our approach to reality must be as well. We ignore form and purpose to our own peril.**
Matthew Lee Anderson is the Founder and Lead Writer of Mere Orthodoxy. He is the author of Earthen Vessels: Why Our Bodies Matter to our Faith and The End of Our Exploring: A Book about Questioning and the Confidence of Faith. Follow him on Twitter or on Facebook.