sarx

What it means

Sarx starts as a plain, physical word. It means meat, skin, muscle, the tissue of a body. From there it stretches to cover the whole physical person, and then further to cover human descent and kinship, so 'my flesh' can mean my relatives or my people. Genesis uses it this way, and Paul does too when he talks about Israel 'according to the flesh'.

Paul then pushes the word somewhere English doesn't naturally go. In Romans and Galatians, sarx becomes a way of describing the whole human orientation away from God, not just the body but the mindset, the appetites, the default direction of a life not shaped by the Spirit. This isn't Paul saying bodies are evil. It's a shorthand for humanity left to itself. One Greek word is doing the work of at least three different English ideas, and no single translation choice covers all of them without losing something.

What English does with it

Older translations kept 'flesh' almost everywhere, which preserves the word's unity but can sound strange in English, as when John says the Word 'became flesh'. Some modern versions, most notably early editions of the NIV, translated Paul's ethical use of sarx as 'sinful nature', which reads more naturally but imports the word 'sin' where Paul didn't put it, and later editions backed away from that choice.

The common mistake

The common mistake is treating sarx as a technical word that always means 'sinful nature' or 'the body as opposed to the soul'. It doesn't. Most of its uses are simply physical or relational, meaning body, tissue, or human descent, with no moral charge at all. Only in a cluster of Pauline passages does it carry the weight of 'humanity turned away from God', and even there the flesh itself isn't being called evil.