No man can conquer it, because it is an unrestrainable and unbridled evil, full of deadly poison. Saint Mitrophan interprets this saying in this way.
Here the divine James speaks in a heightened image. He does not mean to show that it is impossible for a man to conquer his tongue and not sin in word.
Rather, he shows how difficult it is to conquer it. Truly, this work is so difficult that many times even the righteous and blameless sin with the tongue when they do not pay proper attention.
As it is written in Job: "If I am righteous, my mouth will commit impiety; if I am blameless, I will be perverse" (Job 9:20).
That it is not impossible for a man, with God's help, to tame his tongue and not sin in word, David showed when he said: "I said, I will guard my ways, that I may not sin with my tongue" (Ps 38:1).
The venerable Pambo also showed this, as we have said above. James himself showed it when he said: "If anyone does not stumble in word, he is a perfect man" (Jas 3:2).
Those who are perfect and attentive have attained, do attain, and will attain, by the grace of Christ, the state of not sinning in word.
Such people love silence by free choice, or are by nature sparing in speech. But for those far from perfection, inattentive, and talkative, it is extremely hard to conquer the tongue and not sin in word.
Therefore the brother of God says here that no man can tame his tongue. That is, no passionate man can do so by human and earthly effort, while under the influence of pleasure, as Saint Mitrophan interprets.
Sometimes a man's inner disposition passes into a name for him. Thus the Lord said to Peter: "Get behind Me, Satan; you are an offense to Me, for you do not think the things of God, but the things of men" (Mt 16:23).
This means fleshly people and lovers of this life, who love the things of this world.