I'm going to put forth the hypothesis that Otto H. Schindewolf's "types" and Aristotle's "forms" are equivalent terms when it comes to biological organisms.
This marriage of Schindewolf's saltational theory of evolution with Aristotelian metaphysics is my attempt at building a framework for, what I would call "Thomistic ID". "Thomistic" because Thomas Aquinas (possibly the greatest Christian philosopher of all time) took Aristotle one step further - fully integrating Aristotelian metaphysics into Christian theology - and "ID" because the questions I'm going to ask are scientific questions (though in a metaphysical framework) directly related to the Intelligent Design debate.
First off, Aquinas settled for himself (and a lot of others) the proof of God's existence and the design of nature in his "Five Ways" or "Five proofs of God's existence", so there is no need for the Thomist to speculate about whether something that is "complex" has to be designed. That's not what this is about. This is all about "potential". I'd like to focus in particular on Aquinas' concept of active and passive potential: In Aquinas' view, something that has active potential to become something else can do so without the need for God's intervention, but something that has only passive potential to be something else can only do so if God intervenes.
Schindewolf, arguably Europe's foremost paleontologist of the mid 20th century, outlined his basic theory regarding the evolution of "types" (characterized by "basic orgainizational and structural differences") which was based on the sudden appearances of major types in the fossil record. In his view, Darwinian evolution could not account for the appearance of new types.
These then are the 2 big questions I have for science:
1. Does one form have the active potential to evolve into another?
2. Do non-living materials have the active potential to become living organisms?
The answers can only be settled by scientific inquiry - through experimentation and observation. If we, or any other created force, can cause either of these things to occur, then (according to thomism) God's direct intervention was not required. If we cannot, through repeated attempts, make either of these happen, we can then assume that these things possess only passive potential and must therfore (again, according to thomism) be activated by God.