When the matter of a phenomenon is given to us, the understanding proposes to itself three questions: 

1.  How does the fact manifest itself? what is the mode of its existence?  The answer gives us the law of the phenomenon.  Bodies fall to the ground at a determined rate of speed:  the determination of this rate is the law of their fall.

2.  What is the real effective power which produces the phenomenon?  This is the inquiry after the cause.

3.  What is the intention which presided at the production of the phenomenon?  This is the search after the object, which philosophers call the final cause.

What we call understanding or explaining a fact, is answering these three questions; it is finding the law, the cause, the end.  This analysis was made by Aristotle, and seems to have been well made.  The science of nature, as it is conceived by the moderns, does not undertake to satisfy entirely the desires of the human mind.  It confines itself to the first question; it classes phenomena; it then seeks their law; arrived at this, it stops.  The cause and design of things remain out of the sphere of its investigations; the question of God therefore continues foreign to it.

A story is told that when Buonaparte expressed his astonishment that the Marquis de la Place could have written a large book on the system of the universe, without making any mention of the Creator, the learned astronomer replied to his sovereign:  “Sire, I had no need of that hypothesis.”  The answer is admissible if we regard only the science of nature.  An astronomer has no need of God in order to follow out the series of his calculations, and compare their results with the course of the stars; a chemist has no need of God in order to ascertain the simple elements combined in composite bodies; a natural philosopher has no need of God in order to determine the laws of waves of sound or of electric currents.  The science of nature does not demonstrate the existence of God; still less can it deny His existence.  To deny God, it would be necessary for science to demonstrate that there is no order, and consequently no cause of the order to discover; for when we point out the harmony of the universe, we manifestly prepare a basis for the argument which, from the intelligence recognized in the phenomena, will infer the intelligence of the Power which governs them.  To prove that there is no order would be to prove that there is no science.  For any one who well understands the value of terms, the words atheistical science contain a contradiction; they signify science which proves that there is no science.