ID does not claim complexity by itself is an indicator of intelligence.
An instance of complexity by itself while improbable is not an indicator of design. For example, let's say you have a rock in your hand. The probability of that rock looking exactly as it does is highly improbable. The exact surface form, size and weight of that rock is made up of so many possible combinations that it is highly improbable that you will pick up another exactly like it. Yet, the total set of all rock combinations is huge, and when we pick one rock up we know for a fact that it has to take some form. The problem is the rock is unspecified, therefore no one is surprised when we pick up that rock.
The ability to show that the complexity we see is specified increases our suspicion greatly as to how that rock could have come to be. Something is specified if it matches a predetermined pattern. Predetermined in the sense that before we look at the rock we specify the pattern. Suppose we pick up a rock and it kind of looks like a face. Depending on how closely it matches what we know to be a face will depend on how suspicious we are that the rock is an example of specified complexity. No one questions whether the rocks on easter island were created by intelligence or not.
If we find specified complexity that is also functional in some way, that is, it serves a purpose that matches a predetermined pattern, we can increase our belief that this did not arise from necessity or chance. DNA is an example of functional specified complexity. DNA has encoded in it the information needed to produce nano technology.
An instance of complexity by itself while improbable is not an indicator of design. For example, let's say you have a rock in your hand. The probability of that rock looking exactly as it does is highly improbable. The exact surface form, size and weight of that rock is made up of so many possible combinations that it is highly improbable that you will pick up another exactly like it. Yet, the total set of all rock combinations is huge, and when we pick one rock up we know for a fact that it has to take some form. The problem is the rock is unspecified, therefore no one is surprised when we pick up that rock.
The ability to show that the complexity we see is specified increases our suspicion greatly as to how that rock could have come to be. Something is specified if it matches a predetermined pattern. Predetermined in the sense that before we look at the rock we specify the pattern. Suppose we pick up a rock and it kind of looks like a face. Depending on how closely it matches what we know to be a face will depend on how suspicious we are that the rock is an example of specified complexity. No one questions whether the rocks on easter island were created by intelligence or not.
If we find specified complexity that is also functional in some way, that is, it serves a purpose that matches a predetermined pattern, we can increase our belief that this did not arise from necessity or chance. DNA is an example of functional specified complexity. DNA has encoded in it the information needed to produce nano technology.