A mirror is something that reflects back to you. Some mirrors may be distorted and reflect back to you as fatter or thinner or greener or wonkier than you really are. Mirror of the mind is something that reflects your mind back to you. I’m thinking of three ways this can happen. Through a really good psychoanalyst. Through “say back” when you are expressing something and someone does the “I hear you saying…” and also journaling, when you’re able to look back and see attitudes etc. Also another way is through situational analysis and/or self reflection. All this requires a certain receptiveness though and an openness and a willingness to see yourself objectively or as others see you. It requires a certain self awareness to interpret yourself to yourself. Maybe even training of some kind (“And so I tell my life to myself”) and the ability to process things that may be tough to see and hear. That I suppose is mirrors of the mind. I suppose you can mirror someone else’s mind to them or have them do it by using a set of heuristics - identitying their own biases. Have to be careful with this though. It also needs to be done gently and intentionally.