Why can't a person clean up their sin-bent personality on their own?
A person cannot clean up their sin-bent personality because the root problem is not merely what they do but who they are: sons of Adam, born in Adam’s fallen condition. The sin-bent personality may attempt self-improvement, but until God does what only God can do, every effort is ultimately for nothing.
Les teaches that the Holy Spirit moves upon the population and convicts men by the Law of their need, because they cannot do it on their own. He explains through Paul that the root problem is not what we are doing but who we are—sons of Adam. Every baby born into the world comes in the same place Adam was after he fell, with a sweet, innocent little body and its five senses, but lying with them is a personality that is sin-bent. That personality can try to clean itself up, as we have seen and experienced, but until God does the things only God can do, it is all for nothing.
Why is it useless for the sin-bent personality to try to clean itself up?
Because the problem is not merely outward behavior but identity: every person is a son of Adam, born with a sin-bent personality. Self-reformation cannot change that root condition. Only God can do what is necessary, so any attempt by the sin-bent personality to clean itself up is ultimately for nothing.
What must happen before a person's attempts to clean up the sin-bent personality amount to anything?
Until God Himself does the things only God can do, all efforts of the sin-bent personality to clean itself up are for nothing. The root problem is not merely what a person does but who they are as sons of Adam, so human self-reform cannot accomplish what divine action alone can.