Thoughts are the movements of the mind which can be motivated by:
1. God and His angels or even by His servants, ie the saints. from which pure & positive thoughts are always generated.
2. Befallen angels (demons) always transmit impure, negative & passionate thoughts, while on the other hand imposing a state of confusion, despair and agitation within the soul. This occurs as the nature of the angels whether of Light or of darkness, have a very close resemblance to the nature of the state of our soul and thus interact alternatively.
3. The mind can generate thoughts on it’s own accord. These thoughts, good or bad, are dependent upon on the state of the minds illumination or passionate disposition.
We cannot hinder these thoughts from invading our mind, but it must be noted that these are free from sin because all these are at the initial stage, let’s say a simple proposal, a simple image, good or bad. Here the question arises: Will I accept this proposal or will I compose myself with this movement of my mind and reject it’s incitement?
This is the discrimination or discernment which leads us to the very doors of Heaven or Hell, for both are in actual fact the by-product of our own free will’s disposition.