This is what I see 1 John 3:5-10 and other verses is talking about. Verse 8 and verse 10 confirm it. (see passages in red below). They cannot possibly make it more clear that this passage is not talking about two natures in one person (though that is found in other places), it is talking about two different sorts of people.
They do not say that a Christian is sinless and an unbeliever is as evil as they can possibly be. These verses are talking about a person walking according to their nature. A Christian has a new nature and an unbeliever doesn't. It's not talking HERE about two natures in one person, it's talking about two different kinds of people with two different kinds of nature. Interpret the passage in it's OWN context before you interpret it using ideas from another context (like Romans 8)
But if anyone disagrees, we can agree to disagree.
1 John 3:8- He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
1 John 3:10- In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.
I told you before, learn to define your TERMS. WE do not all MEAN the Same thing, even though we use the same TERMINOLOGY. I do not know for sure what you mean by two Natures in ONE PERSON. I can GUESS what you mean, but that is how the CONFUSION gets started. If I was to GUESS, it would be the two Natures that PAUL DESCRIBED.
Romans 7:17-25 (HCSB)
17 So now I am no longer the one doing it, but it is sin living in me.
18 For I know that nothing good lives in me, that is, in my flesh. For the desire to do what is good is with me, but there is no ability to do it.
19 For I do not do the good that I want to do, but I practice the evil that I do not want to do.
20 Now if I do what I do not want, I am no longer the one doing it, but it is the sin that lives in me.
21 So I discover this principle: When I want to do what is good, evil is with me.
22 For in my inner self I joyfully agree with God’s law.
23 But I see a different law in the parts of my body, waging war against the law of my mind and taking me prisoner to the law of sin in the parts of my body.
24 What a wretched man I am! Who will rescue me from this dying body?
25 I thank God through Jesus Christ our Lord! So then, with my mind I myself am a slave to the law of God, but with my flesh, to the law of sin.
Now to me, that is the DUAL NATURE of a Christian. Sure as we study HIS WORD, we will see the Nature that wants to do GOD WILL, getting Stronger, and Stronger, to Dominate the Will of the Flesh, but will not get rid of the Sin Nature until the Resurrection.
You do know that JOHN prefers to us the
Greek Present tense VERBIAGE, so most of the verbs in
1 John, are implying a lifestyle of doing that Verb, not the Perfection of that Verb. Something that we do not have in ENGLISH. For example.
1 John 2:4 (NASB)
4 The one who says, "I have come to know Him," and
does not keep His commandments, is a liar, and the truth is not in him;
Because the verbiage is Present Tense in the GREEK, it implies NOT PERFECTION, but a lifestyle of Striving to Keep His commandments.
That may be why you are not seeing what it actually says.