If you read Week 2, Mr. Haanel mentions the functions of the conscious mind, which are; discrimination, power of reasoning, the seat of the will and the ability to impress the subconscious. He also mentions the values of the subconscious mind, which are; that it is enormous, it guides, warns, controls the vital processes and is the seat of memory. All of these functions and values would appear to be quite powerful resources. I hope this helps.

I just want to add one thing to what Paul said. Haanel also said "subconscious mind is instinctive desire, the result of past reasoning will". Desire is obviously a very essential element in the Master Key System.