This criticism was made, for example, in:
- Levit, Georgy S., Hossfeld, Uwe and Witt, Ulrich (2010) Can Darwinism Be “Generalized” and of What Use Would This Be?
variation, selection and inheritance [...] are but an empty hull that lacks own explanatory substance.There's a sense in which this is true. The problem is with the "mutation" operation. Unconstrained mutation predicts everything and is useless.
Neo-Darwinism avoids this issue - by claiming that mutations are "undirected". However, this is not really an acceptable approach in cultural evolution - where it is widely agreed that mutations are not remotely random - and that modeling them as being "undirected" is a coarse and limited approach.
I generally attribute the correct resolution of this issue to Donald Campbell. He basically said that variation was generated on the basis of existing knowledge. He used the unfortunate term "blind" to describe this - which has led to endless misunderstandings of his idea by confused critics.
Gary Cziko's terminology from the title of his book, without miracles is another approach to the problem. The term "without miracles" expresses the idea that mutations should be explicable naturalistically. While naturalistic explanations are good, scientists normally take it for granted that their explanations should be plausible within a naturalistic framework. The idea that mutations do not involve "miracles" isn't really all that much of a constraint - and the more scientific theories constrain expectations the more valuable they are.
This article tries to answer the question of what the minimum constraints on mutation are that avoid the accusation that the resulting theory is vacuous. The answer is pretty simple: all that is necessary is that mutations should be limited. If an evolutionary sequence requires mutations that exceed the mutation limit, they violate the predictions made by the theory.
This constraint is even weaker than the requirement that mutations should be naturalistically plausible. On one hand the idea of mutations being limited (in some specified way) is vague and not very useful. However it does show how easy it is to avoid the accusation that Universal Darwinism is empty and vacuous. Just put a limit (any limit) on the type of mutations permitted by the theory, and you have a falsifiable theory.