1. A Great World Cannot Be Placed Within a Small One
Assume that you are seated beside the sea and behind it are extremely high mountains. The roaring waves and the shaking of the water against the shore and with great strength, return to the sea. We look at this scene for a moment. Then we close our eyes and see this scene in our minds with all of its greatness. This shows that other than a body and cells of the brain, another jewel exists which can reflect any design no matter how great and at any scale. Clearly, this jewel must be something which is beyond the material world because we find nothing like it in the material world.
2. The External Particularity of the Spirit
We have many chemical and physical properties in our bodies, the motion of the heart has a physical quality but the effects on food is a chemical substance and examples like this are many in our body. If the spirit, thought and reflection were all material and had physical and chemical quantities of the brain cells then why among them and our other physical properties is there a great deal of difference? Our thoughts, ideas and spirit relate and connect us to the external world and make us aware of that which passes outside but the chemical particularities of the stomach and the physical motion of our eyes and tongue and heart never has such a state.
3. Experienced Proof of the Originality and Independence of the Spirit
Fortunately, today scholars by various scientific and experimental means have proven the originality and independence of the spirit and permanently answered those who deny the truth of the independence of the spirit and all people who believe it to be material. Hypnotism is among the clear reasons for this which the experiments have proven this. We see dreams and scenes appear in our dreams which sometimes speak of the future and sometimes they clarify something which had been ambiguous in such a way that it cannot be called chance or accident which is a further proof for the independence of the spirit. These examples show that the spirit is not material and that it is not the result of special physical or chemical properties of the human brain but rather it is a metaphysical truth which does not end when the body dies but, instead, prepares itself for the Day of Resurrection and the Hereafter.
Ref: Fifty Lessons of Principles of Belief for Youths; Ayt. Makarem Shirazi; Translated by: Bahador Shirazian; Published by: Ahlul Bayt World Assembly