The heart is the wellspring of life. It directs thought, speech, and actions. If it corrupt, so is every thought, word and action.
I want to be clear here. This doesn't mean every thought, word or action is wrong or evil. But it does mean that every thought, word, and action flows from an evil source.
I also want to be clear that evil as defined by God doesn't mean wicked or dastardly, though these are found in man and are included in the spectrum of evil. What makes that which flows from the heart evil is that it has no connection to God as its source.
Consider for a moment how God created us physically. We need oxygen at least every 3 minutes or we die. We need water every 3 days or we die. We need food every 30 days. Physically, we are dependent on God for these things continually or we die. If it's true that the unseen things of God are known by the things that are seen, what might the separation of man from God mean spiritually? How might the heart of man that was designed to be sustained and nurtured by God be altered when God is no longer its source? How might man's thoughts, words, and actions be altered? And what might be required in man for this to be restored to man?
The heart is invisible, intangible inner man (the soul and spirit) that inhabits the physical, tangible outer man (the flesh).
The spirit of the Christian is perfect and pure, but his mind still needs ongoing renewal, and his body needs to be kept in check by the perfect spirit and the renewing mind until it is changed at the resurrection.
I think we agree that both the inner and outer man are imperfect and diseased. The inner is imperfect because of the imperfect thinking and the body because our instincts are opposed to principles expressed in the Sermon on the Mount. Total depravity is a misnomer. Even Calvinists deny "total depravity" is true, but rather than be honest and rename their theory to correctly describe their actual beliefs, they use the words "total depravity", but claim the words together do not mean for them what they literally do mean. They want to change the meanings of words, rather than choose correct words. Such dissimulation cripples attempts at clear communication.
Can we agree that an apple that is more than 0% rotten is a bad apple?
Can we agree that an apple that is 90% rotten is a bad apple?
Can we agree that the 10% of that last apple is good, even though the apple is bad?
Can we agree that it is possible for a seed taken from a bad apple to produce a good tree?
Can we agree that we could possibly make a good apple pie from the good parts of 20 bad apples?
Can we agree that the Holy Spirit in our perfect Christian spirit is a spring that we can access to produce good?
Can we agree that our unrenewed soul/mind is also a spring that we can access to produce bad?
Can we agree that both our spirit and our soul are in our heart?
Can we agree that we therefore have two well-springs in our heart, not one.
Can we agree that, depending on which source we rely upon as the source of our thoughts, imaginations and actions, we are capable of either good or evil actions, thoughts and imaginations?
Can we agree then that good untainted actions can come from the good parts of a bad person, if they source their actions from the good wellspring?
Can we agree that we being
x% bad, are not good, but are bad. And God who is 100% good is good and not bad?
As a starting point for an continuing honest and frank discussion, could you please answer each if these questions, so we have some clear ground of agreement and disagreement to work from and discuss further? Could you please answer the questions yes or no, and then qualify your answer if you need to do so?