A repentant man turns from previous violation of law, and accepts every new law that may be revealed to him. Repentance is obedience; and the repentant person is always ready to obey righteous laws.
Baptism is one of the laws of the Kingdom of God. "Except ye repent and be baptized ye can in nowise enter the Kingdom of God." The repentant person must of necessity accept this law with the others with which he may be familiar.
[Sidenote: The equivalent of baptism found in science.]
Students of science, who agree that faith and repentance have a place in science, frequently assert that the equivalent of baptism is not found in external nature. This claim may be proved false by examining the nature of law.
The chemist must frequently produce the gas hydrogen. To do it, an acid must be poured upon fragments of certain metals. In thus producing the gas, the chemist obeys law. The astronomer who studies the stars discovers that by using a piece of glass properly ground, his powers of vision appear to be strengthened. He therefore prepares such lenses for his telescopes, and thus obeys law. The surgeon uses antisceptics in the treatment of wounds because he has learned that such application will destroy germ life, and thus the surgeon obeys law. The electrician has found that by winding a wire in a certain manner around iron and rotating it near a magnet, electric currents are set up. He builds dynamos according to such principles, and thus shows his obedience to law.
It must be noted that the scientist does not know just _why_ acid added to metal produces hydrogen, or _why_ a certain curved lens brings the stars nearer; or _why_ certain chemicals destroy low forms of life or _why_ wire wound in a certain way when rotated in the magnetic field will produce electricity. Nature requires, without volunteering an explanation, that to produce hydrogen, see the stars, destroy germs and produce the electric current, certain invariable laws must be obeyed.
Baptism is essentially of the same nature. To enter the Kingdom of God, a person must be baptized. Just _why_ baptism should be the ordinance that opens the door, no man knows. It undoubtedly has high symbolic value; but the symbolism might be expressed in many other ways. All that man can do is to obey.