One of the sobering realizations of recent years has been the discovery that a large fraction of the matter in galaxies is unseen. As discussed by Freeman (this conference), the evidence for this dark matter is overwhelming, and we are forced to conclude that most of what we see in galaxy morphology may only be like icing on a cake. However, this icing makes galaxies more interesting than they might otherwise be and it offers a lot for understanding galaxy structure and evolution. It seems clear that external influences can drive morphology in a variety of different ways, from gas stripping, accretion, and mergers, to tidally generated bars and spiral structure. Natural formation of bars and spiral patterns can probably also occur, and the influence of the orbital resonances of these non-axisymmetric disturbances can add further complexity to what we see. Morphological classification has many limitations and can only be used as a guide to understanding the underlying dynamics. However, even though it can be misleading, classification is still alive and well in the 1990's, as evidenced by the publication of the RC3. Now, for the rest of a conference like this, we have to weigh the evidence for nature vs. nurture in influencing galaxy structure and evolution.