In light of Aquinas's teaching, I first critique William Dembski's mathematical approach to design in nature, and then critique Michael Behe's failure to distinguish between causes that physically produce an object and causes responsible for the plan for that object. I then investigate Aquinas's Fifth Way, both comparing it to Paley's argument, and attempting to discern where it disagrees with atheistic accounts of evolution. I show that Aquinas acknowledges that living things can result from finality at one level and chance at another level; in other words, he acknowledges that contingent intermediary causes are able to be part of God's plan or design for the production of new species. Thus, the disagreement between Aquinas and the proponents of atheistic versions of evolution is not due to any denial on his part that chance may have role in the production of new species. I then show that even atheist biologists and philosophers recognize a regular tendency in nature to something good, namely, the tendency for niches to be filled, resulting in the good of biodiversity. Where they and Aquinas part ways is as to whether things that lack cognition can only tend to an end when directed by an intelligent being.