According to Buddhism, all phenomena of the universe coming and going momentarily and unceasingly at all times are illusory and unreal.
The reason why we cannot see the reality of those phenomena is this; instead of looking at them objectively, we are so much blindfolded by our subjective thought, which is our habitual way of thinking, that we are misled to think the petty self known as “Ego” to be the true “I“.
Under the delusion of greed, pride, stupidity and egoism, to take the body, family and things to be our belongings, and thus when we are deluded externally with the phenomena and internally with the mind, we become so much attached to our ego and our belongings that for the purpose of keeping them by all means.
We may do any evil, even to lie, slander, attack and harm others.
The force of such perverted activities of the body, speech and mind caused by delusion is in Buddhist terms called “Karma“. At first, the karma turns in keeping with the external influence of the phenomena but later having expended its power passively, unconsciously, and become sufficiently “fumed”, it turns to inward development and the longer it is fumed in this manner, the more powerful and the more harmful it will become.
Extended readings: The Six Paramita