it's not that alone. it would be first identifying things in nature that can be defined as systems, such as the water cycle. then noting how these systems are intricate, and interlocking. we can note the roll and purpose of the individual parts of a system. after examining all these factors together, we can start to make a case for ID. A comparison between said natural system can be made to something we know for sure has been designed, like by humans, for example.
there's a lot it. it's far more than "it's complex, so mydietydidit".
Philosophically, this runs into problems with what's called the
anthropic principle, which essentially states "Anything necessary for the existence of intelligent life must exist, or else we wouldn't be here to talk about it"
If a water cycle is necessary for the existence of complex life, then complex life would only arise on a planet with a water cycle. Therefore, it should be no surprise that we live on a planet with a water cycle, if we didn't we'd never have been born. This situation might be compared to a puddle of water in a hole commenting on how lucky it was to find a hole the exact shape of the puddle.
Due to the anthropic principle, the
probability of anything occurring that can be shown to be necessary for complex life is truly irrelevant. The question becomes, is there anything that we know about a water cycle that is
actually impossible and
not simply improbable from a standpoint of meteorology.
in my estimation, you have three options:
Either assert A) A water cycle requires additional* supernatural effects to either sustain itself come into existence
( *by "additional" i mean, in addition to any supernatural effects, if any, that were already necessary to cause the big bang, the creation of stars, planets, etc or to create the natural laws of the universe. )
To assert A and be taken seriously you should point out what part of the water cycle is not naturally possible.
or assert B) A water cycle is so unlikely and fortituous it must have been designed
in which case i would point to the billions and billions of other stars and billions and billions of galaxies that we can see, in the sky... and those are just the ones we can see, for all we know the universe expands infinitely in all directions. Then i'll say, as i already said, if something so fortuitous as intelligent life did not arise on earth, lucky or not, we wouldn't be here to talk about it.
or you could assert C) The physical laws of the universe were
designed such that a water cycle, intelligent life, etc, was the inevitable result.
In which case you'd basically be a Deist and you'd have no problem at all with evolution.