The evolutionist, we have pointed out on other threads, builds his platform on a logical redundancy.
When you ask him how such and such evolved, he will answer you with a description of its current utility, and suggest that those without such utility were culled by natural selection. As we have pointed out, his position is summed up by the parody "post hoc ergo propter hoc", which is to say "after the fact, therefore before the fact".
But evolutionists have trouble grasping abstract concepts, so this thread is designed to put the issue into a simple framework.
Let us use the number '4' to represent the current state of a supposed evolved entity.
Let us use the number '1' to represent a catalytic situation, or some assistance/partnership, on route to the number '5'.
Let us use the number '5' to represent an intermediary utility/purpose of '4'.
Let us use the number '10' to represent an ultimate utility/purpose of '4'.
The dialogue:
Creationist: "how did '4' evolve?"
Evolutionist: "because '4' had an advantage over '3': it could combine with '1' to form '5', instead of having to combining with two lots of '1'".
Creationist: "so?"
Evolutionist: "so '5' was needed because it fits exactly two times into '10'!".
Creationist: "but that is only so because '10' divided by '2' produces '5'! Why is it that '10' exists in the first place? Where did it come from?"
(The evolutionist, realising there is something missing in his reasoning at this point, but not really wanting to find out what, immediately invokes his higher-than-usual evolved thought-blocking ability, and declares proudly but irrelevantly: "natural selection!".)
For over a century now, we have still not heard from the evolutionist the reason for the existence of '10'. In the absence of such explanation, all he is doing is working within the confines of a superset called "purpose" of which he is unaware. Accordingly, his argument is nothing more than a living corollary. It is redundant from the very start.