This summer I will be studying Philosophy of Nature through International Catholic University. This course ought to be pretty interesting, because it is the topic I find myself thinking about most often of late. Strictly speaking, philosophy of nature is the study of natures, or essences. However, in practice when we mean philosophy of nature we mean something close to, but separate from modern science. Natural philosophy seeks to explain things in terms of their causes. For an Aristotelian, that causal agent is a nature. Modern science looks for causes too, but typically doesn't explicitly conceive of a thing that embodies the causes studied. I was thinking of something like this when I posted the cartoon about the difference between scientists and normal people. If you want to know the nature of a thing, a good question to ask is indeed, "I wonder if it does that every time?"
For a long time, earning a doctoral degree in physics meant the study of natural philosophy. The practice of referring to the field as natural philosophy persisted long after anyone actually studied natural philosophy as part of a program in physics. I don't remember where, but Fr. Stanley Jaki once said that it took far too long for this change to be made, and it retarded the progress of physics because people were pretending to do something they were not in fact doing. Fr. Jaki posited a pretty strong separation between what modern, quantitative science could know, and the knowledge of philosophy. Fr. Jaki argued that the quantitative methods of modern science made it impossible to bridge the gap to knowledge of natures, so science and natural philosophy were forever sundered.
At least from the looks of it, my current course takes a different tack. The textbook is by Fr. William A. Wallace O.P. (Freedom!, no just kidding, not that William Wallace) It is about unifying philosophy of nature and philosophy of science through modeling, by which Fr. Wallace means a variant of the kind of probable reasoning that is common to both Aristotle and modern science. However, being in the Aristotelian tradition, Fr. Wallace argues that we can rise from probable reasoning to more certain knowledge of natures. This ought to be pretty good. Like Fr. Jaki, Fr. Wallace has experience in science. Wallace worked at the Naval Research Laboratory and studied electrical engineering and physics.