First fundamental:

The spirit is eternal, and the First Aim's proofs for the existence of angels and other spirit beings prove its eternity. We are too close to the souls of the dead, who are waiting in the barzakh[1]to go to the Hereafter, to require proof of their existence. If such beings have the necessary insight into the reality of things, saints may see and even communicate with them. In addition, almost everyone encounters them in true dreams. As modern materialism causes doubt in such obvious matters, we provide four sources from which persuasive knowledge can be obtained.

[1] The intermediate world between this world and the next. (Ed.)