Internalism and Laws of Form 259
represent traits that, at their origin in an ancestor, arose as either adaptations or
constraints. Nonetheless, the immediate form of an organism can still be
meaningfully parsed into three major contributions of current adaptation, current
constraint, and historical inheritance—Figure 4-5. This insight has generated the
various "triangular" models of evolutionary causation that have gained vogue in
recent years (see Fig. 4-6).
These issues and parsings have pervaded natural history since Plato and
Aristotle argued about abstract form vs. teleology. Darwin made a seminal
4 - 5. Because constraint and adaptation act either from the past or in the present, we may
envisage three primary determinants of present form: present constraint, present adaptation, and
inheritance due to past history of either constraint or adaptation.4 - 6. One of a group of "triangular" models constructed to express the major influences upon the
genesis of form. The three vertices of this triangle refer to the three influences depicted in Figure
4 - 5.