So I've been reading through the Phaedo and have been thinking about Plato and have come up with a question, before I ask the question, I will give some background.
Plato's theory of the forms (as I understand it) is an attempt to explain why particular things all partake in the same universal (or have shared properties). An example question is "why is it that all dogs have roughly similar properties? What causes this to be the case?" The theory of forms explains this by positing a great number of theoretical and unobservable entities called forms. So for instance there is a form of dog. What exactly this form of dog is (or any of the forms for that matter) Plato does not say, but what he does say is that the form of dog is the casual force which makes all particular instances of dogs similar in properties.
Now with modern science, a genetic and evolutionary explanation is a much more commonly accepted explanation as to why dogs (and living things generally) have the same properties and features. Different genes and DNA give instructions to cells telling them which proteins to produce and how to organize themselves in order to create bigger structures. So because dogs have dog genes, a dog structure is produced. So genes are used to give the same explanation that forms do. They explain, for biological things, why those biological things have similar properties and characteristics.
So my question is generally this "why is it that a genetic / evolutionary explanation of similarities is better (if it is better at all) than Plato's explanation of forms being the casual agent in creating similarities between species?"
I think there are a few answers to this question and I would be interested in hearing what you all have to say, but I would also be interested in receiving some thoughts on whether: Answer 1: Explanations that do not posit unobservable entities are weaker theories than theories that posit observable entities.
This seems like it might be true but I can't say exactly why. Can anyone explain this to me in more detail?