Romans 8:6

For the mind of the flesh is death; but the mind of the Spirit is life and peace.

Mind of the flesh ... cannot be thought of as identifying the mind with the flesh, that is, the substance of the flesh. Tertullian cautioned that

The carnal mind must be referred to the soul (as distinguished from the flesh), although ascribed sometimes to the flesh (as here), on the ground that it is ministered to by the flesh and through the flesh.[13]

The "mind" that Paul had in view here is the rebellious and perverse spirit of man's inner self; and the meaning is not primarily that physical death is caused by such mind (though, of course, it can cause that also), but that a state of death derives from and automatically accompanies such a mind, a condition called death "in trespasses and sins" (Ephesians 2:1). In a simplistic view, man's entire trouble lies in his inmost mind. Who is in charge there? If the inner throne is occupied by Satan, sin and death reign. If Christ is on the throne, life and peace reign.