I believe that the current controversies regarding "intelligent design" are best understood in light of Aristotle's theory of the four causes. He concluded that there are 4 types of cause: formal, material, efficient and final. The formal cause of something is the pattern, design, or archetype that determines the final form of the thing. The architectural plan for a house or blueprint of a machine are examples. The substance that actually makes up the thing, the bricks and mortar of the house or metal of the machine is the material cause. The efficient cause is the factual production of the thing; the building of the house or assembling of the machine, and the final cause is the reason why the enterprise was undertaken in the first place, e.g. somebody needed a house or the machine was thought to be useful.
The contemplation of the biological origin of man also demonstrates each of Aristotle's four causes. Genes are the formal cause of homo sapiens, ribonucleic acids are the material cause, evolution or natural selection is the efficient cause. These observations seem to involve little controversy. The issue arises when people consider the final cause, the "why?"
The final cause (in the Aristotelian sense) creates contention when included in scientific thought because it is not science. It is irrelevant to understanding the other three types of causes, and is not amenable of scientific investigation. Those who wish to introduce an "Intelligent Designer" as the final cause of man conflate philospohical and religious yearning with scientific empiricism, ending up with something that is neither intellectually or spiritually fulfilling.
People search for a final cause of their existence, not because it is scientifically necessary, but because it is emotionally comforting. Piety would be so much easier if the objects of our devotion could be accessed by more familiar forms of reasoning. Faith would be much easier if it didn't require so much faith.
Ultimately, intelligent design will be found irrelevant to both the science of biology and the destination of a true spiritual journey.