Otherwise, if the active cause were not determined to produce some particular effect, it would not produce this rather than some other. In order to produce a determined effect, it must, therefore, be determined to something in particular which serves as an end. Efficient causes are not indifferent, and their effects are not fortuitous. As a matter of fact, from the many individual activities of the various beings of the world order and harmony result in the universe. And when different forces converge toward a harmonious result, their convergence cannot be explained except by admitting that they tend to realize a plan.
Life is essentially teleological.
There is a co-ordination of all the organs, the functions of every one depending on those of the others, and tending to the welfare of the whole organism. Little by little the primitive cell develops according to the general type of the species and evolves into the complete organism. But what is not explained by mechanism is the convergence of many different causes toward a given result. If organs are so many mechanisms, it remains to be indicated how these mechanisms were organized. If appeal is made to evolution, it must be remembered that evolution is not a cause, but a mode of development, and that organic evolution rather accentuates the need of final causes.