Sechel and Dimayon
The Chazon Ish believed that it was important for an individual to use the mental faculties he was given. He calls this, שכל, “Sechel,” or the use of one’s intellect.
He did make a very important point about the manner in which one uses his intellect. He cautions us that we be able to make the distinction between “Sechel” and “Dimayon,” which would be translated as “imagination.”
This refers to where the mind plays tricks on us. It convinces us that certain things are true, when they are not. We convince ourselves that these things are true, when it is all in our imagination, or “Dimayon.”
This is what might make someone obsessed with acquiring material wealth. His Dimayon convinces him that this is a worthy pursuit, even if it means neglecting his wife and children.
The mind can clearly play tricks on us. The Chazon Ish is warning us not to allow ourselves to be misled by our Dimayon. It might be a trick of the Yeitzer Hara to get us off course.
When we allow our Sechel to guide us, we are tapped in to a spiritual connection with Hashem. He will guide us on the correct path that will lead us to real joy and peace of mind.
The beauty of studying such books of philosophy, allows us to understand ourselves better, and helps us take the proper precautions to stay on the correct course in serving Hashem like we should.