The internal communication of ideas, words and notion within the mind. The thoughts that people create often become their reality.
Because thoughts cannot be seen, there is generally no perception that they have form and shape. However, our mental patterns rise like flames from a fire, along with an actualizing desire. These patterns seek form, even when they fall, but are not of any recognizable form, and may connect to realities other than our immediate one.
Thoughts are like cells, in that they have their own structure and seek their own fulfillment. Even each cell within the body is altered by a thought to a certain degree, which in turn alters one's environment. The brain and body subsequently responds as it is conditioned to behave. This creates a dynamic situation where subsequent thoughts can engage to perpetuate further cellular responses. If there is a limiting factor, it is contained within our perception of reality and expectations. Ultimately, we individually choose to experience one of the probable events, while other events are actualized in another reality or time sequence.
As thought is energy, and energy cannot be destroyed, this is proof that there is some form of existence after physical death.