Have you ever thought of yourself as an idea? What is an idea, anyway?
To illustrate, I am going to mention a word: apple. What mental picture did you have when you read that word? It is an idea in your consciousness. Now, if it is raining, does the apple in your thought get wet? If it is hot outside, does it go bad? If there is a plague of worms, is your apple ruined? In all these instances it remains untouched.
So an idea is a form of thought without a material structure. No physical condition can affect it. Why is this? Because an idea is in our thinking, so our thought controls it. Since each of us is a spiritual idea in God, divine Mind, we can reason that Mind controls its own idea. Therefore, in reality, as God’s idea we are not subject to physical conditions or beliefs.