once the mind has been exposed to knowledge, it can't go back to what it was.
Indeed you can't unknow something, but you can ignore what you know and make use of it. Eventually knowledge can fade and have less influence, and you can even forget. It's happened to me and then I come across something and I'm like oh yeah I knew this too but from many years ago and I forgot, or it's influence in my recollection was diminished to the point I never recalled it when thinking about things.
Sure, we have in storage so much information that the useless one gets tossed away. I just wonder about the impact that these tiny influences we have stored deep down have over our decision making. We like to think that we are the masters of our fate, sailors of the mind ship, but decision making is heavily influenced by our secretely stored information/biases. Most of the times they elude us and we can't easily access and wonder why is that stored. I particularly wondered about this after I've read a book called Thinking fast and slow by Daniel Kahneman and I was just stunned of how "unclean" is our decision making in regards to external influences.