Why did Jesus tell a young rich man to keep the commandments to obtain eternal life?

Is the “eternal life” asked for by the young man (Matthew 19:16) the same “eternal life” spoken of by John in his 1 John 1:2, etc? If so, why did the Lord Jesus answer—”Keep the commandments”?

I would judge “eternal life” to be one; there cannot be two kinds, but no doubt there are many manifestations and degrees of it. Eternal life is not mere endless existence, it is that with the added quality of harmony with God. In Psalm 133:3 we read, “for there the Lord commanded the blessing, even life for evermore”, and in Daniel 12:2 that “Many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.” Clearly, the saved of the Gentiles will not enjoy this life in the same degree as the true Israel, nor these as the Church, but all the elect and redeemed will enjoy it in their measure. “This is life eternal that they might know Thee the only true God and Jesus Christ whom Thou hast sent” (John 17:3). It is, then, to know and enjoy God in Christ. “This is the true God, and eternal life” (1 John 5:20). “He that believeth on Me hath everlasting life” (John 6:47). The young man of Matthew 19:16 was using words he had heard, but of which he knew nothing yet by experience. Of course, you can have eternal life without being able to give any account of it, but your relation to God is changed, though you may not be able to define what has happened.

The very needs and cries of an infant prove it has life, and you would not doubt it because the little one could not explain what life was. The Lord, of course, knew all about the young man, his stage of experience and small capacity, and treated him accordingly in His perfect wisdom. He even pressed home the law to its legitimate conclusion—”Thou shalt love they neighbour as thyself” (though this naturally proved beyond the capacity of the Jews), to bring him face to face with his own deep need. Though we do not hear of this young man again, no doubt, “the word that went out of his (Christ’s) mouth did not return void.” We, too, should seek to diagnose the condition of men, and apply to them the right treatment, in order to bring them to Christ.