When the writer of Romans penned these words I think he assumed that his readers would know what evil is. Nowadays that may not be the case:
Is evil a noun or is it a verb?
There is much confusion over that these days. Is evil something that is done by you or to you or is evil something you are? Is it a dark and powerful personal force within you or is it the harmful and hurtful things you do? That confusion contributes to many of our problems in our world today.
If we are going to overcome evil, obviously we must have a clear and actual understanding of what evil is.
A study of the whole 12th chapter will give you a good concept of what evil is.
V.1 - Evil is refusing to surrender your sinful nature to Christ.
V. 2 - Evil is conforming to the "world" or the "cosmos" in your thinking and your values.
Evil is not desiring the will of God.
V. 3 - 8 - Evil is failing or refusing to serve God with your gifts and talents.
V. 9 - 13 - Evil is self-seeking and despising others.
V. 14- 20 - Evil is being conceited, spiteful and retaliatory toward those who disagree with you.
You will either overcome evil or it will overcome you. And until you deal with the evil that controls your nature, you will be overcome by evil.
So, evil is a noun.
It is a nature that dwells in you from the time of your birth. Being born evil you are also born separated from God. And that spiritual separation from God is the essence of your evil.
But, evil is also a verb!
It is because of the evil that dwells in you, evil guides your thoughts and decisions. Evil thoughts breed evil attitudes that are expressed in evil actions.
God calls you to be delivered from evil. You can choose to allow Him to deliver you and cleanse you from evil.
Or, you can be overcome by evil. Which will it be today?