The First Commandment is: I am the Lord thy God, Thou shalt not have strange gods before Me.
Faith: The first obligation laid on us by this Commandment is that of Faith. Faith is the supernatural virtue by which we believe in the existence of God; and in all the truths that His Church proposes to us. Faith is the first of all the supernatural virtues, and the foundation of all religion; because we cannot worship God unless we first know and believe that He exists. "Without faith it is impossible to please God." (Hebrews 11:6)

Faith and Science.
Faith and reason, religion and science,
can never contradict each other. True religion cannot contradict true science, because they both come from God. If, at times, there seems to be a contradiction; if science, for example, seems to contradict the Bible, the contradiction must exist only in the mind of one who is himself in error. Either he has misinterpreted the Bible, or he has misunderstood the facts of science. Reason and Faith both coming from God, are meant by Him to assist one another. Reason and science can prove that God exists. They can also examine the Holy Scriptures, for example, the Gospels, and prove their reliability as historical documents. Reason and science can examine the life and the miracles of Christ, above all the great miracle of His Resurrection, and thus prove that Christ is God. 

Reason and science can examine modern miracles, such as those of Lourdes and Fatima, and prove from them the miraculous intervention of Divine Providence. Reason thus establishes the credibility of the Sacred Scriptures; the Divinity of Christ; and the Divine origin of the Catholic Church. Faith, then accepts the teachings of Jesus Christ and of His church as coming from the God of Truth Himself. Once we know that God has spoken, we believe the mysteries He reveals to us. If we accept the word of men, says St. John, how much more should we accept the word of God? "If we accept the testimony of men, the testimony of God is greater." (John 5:9.) Atheists and infidels sometimes refuse to look at facts; such facts, for example, as the miracles of Lourdes and Fatima; because they contradict their preconceived ideas. These self-styled rationalists, in acting thus, put themselves in the same category of insincere hypocrites as the Pharisees of old, whose one thought, after Christ had raised Lazarus to life, was to put him to death again that he might not remain a standing and visible proof of their own hypocrisy.

The Catholic Church has always been the friend and promoter of science and the enemy of ignorance; because true science is one of her greatest supports. So much is this the case that her enemies, in their attacks from this direction, are limited to one or two favorite names; and even in these cases the fallacy underlying their attacks can be easily exposed. Chesterton relates that an English schoolboy engaged in an argument with a French schoolboy on the respective merits of their two countries, finding himself in difficulties, shouted "Waterloo"; and his victory was final and conclusive.

Eminent among the world's princes of science are found the names of many illustrious Catholics such as Louis Pasteur, who lived and died her devout son, loyal to all the Church's teachings. The words of the Hon. W. E. Gladstone, a Protestant, and one of the greatest statesmen England has produced, may be aptly quoted here: "The Catholic Church has marched on for fifteen hundred years at the head of civilization, and has harnessed to her chariot as the horses of her triumphal car, the chief intellectual and moral forces of the world. her art, the art of the world, her genius, the genius of the world; her greatness, grandeur, glory and majesty, have been almost, though not absolutely all that in these respects, the world has had to boast of. .....She is every day enlarging the boundaries of her vast empire. Her altars are to be found in very clime, and her missionaries are to be found wherever there are men to be taught the evangel of immortality and souls to be saved." 

Source: Commentary on the Catechism, Rev. W. Frean C.SS.R.