A common belief regarding the nature of mankind is that we have a body, a soul and a spirit. This is known as the Tripartite Nature of Man (or [trichotomism](https://en.wikipedia.org/wiki/Christian_anthropology#Three_parts_.28Trichotomism.29)). Some, however, hold to only a Dual nature of man (also known as [dichotomism](https://en.wikipedia.org/wiki/Christian_anthropology#Two_parts_.28Dichotomism.29)).

What is the essential argument in favor of the Dual Nature of Man? It would be interesting to see how the evidence for the Tripartite Nature of Man is explained as well, especially a verse like Hebrews 4:12.

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> For the word of God is living and active, sharper than any two-edged sword, piercing to the **division of soul and of spirit**, of joints and of marrow, and discerning the thoughts and intentions of the heart. Hebrews 4:12 ESV
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