Isa 55:8-9 “For my thoughts are not your thoughts, neither are your ways my ways,” declares the LORD. “As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts."I think you are misunderstanding this verse. In context it is talking about the wicked forsaking his way and the unrighteous man forsaking his thoughts "for my thoughts are not your thoughts, neither are you ways my ways". In other words, God's ways are not wicked, God's thoughts are not unrighteous. That is what this verse is saying. "Let the wicked forsake his way and the unrighteous man his thoughts... for my thoughts are not your thoughts and your ways ar enot my ways..."
This verse doesn't mean that we can't understand God, or that we can't know His mind, or that we can't see His reasoning. It is to twist the meaning of that verse and take it out of context to use it that way.
Actually I believe you're both mistaken.
Look at the context. This is one of the most mis-quoted verses in the bible.
In this passage, God implores the backslider to come back to Him, He says...
Is 55:6 ¶ Seek ye the LORD while he may be found, call ye upon him while he is near:
7 Let the wicked forsake his way, and the unrighteous man his thoughts: and let him return unto the LORD, and he will have mercy upon him; and to our God, for he will abundantly pardon.
8 For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.
9 For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts.
What God is saying is this: Forsake your wicked ways and return unto me, and I will have mercy and grant you an abundant pardon. WHY? HOW CAN WE KNOW GOD WILL RECEIVE US BACK?
"BECAUSE MY WAYS AREN'T YOUR WAYS..."
Mankind don't naturally lean towards 'free grace'. We aren't like God.
Since seeing this passage in it's correct light, it's become to me one of the most encouraging verses in the bible. God is telling us, "I'm not like you. I'll readily show mercy and an abundant pardon if you only come back."
We aren't nearly as gracious. We want our 'pound of flesh'. Not so with God.
To twist this passage to show God angrily demanding righteousness before taking us to Himself is the most gross error.
God is not like us. His thoughts are not ours. His ways are higher. Much higher.
He will show mercy. He will pardon abundantly.
Paul understood this grace well. That's why he had to answer the question in Romans 6:1.
Jer 3:12 Go and proclaim these words toward the north, and say, Return, thou backsliding Israel, saith the LORD; and I will not cause mine anger to fall upon you: for I am merciful, saith the LORD, and I will not keep anger for ever.