Joseph F. Smith, Gospel Doctrine, p.61
The Holy Ghost as a personage of Spirit can no more be omnipresent in person than can the Father or the Son, but by his intelligence, his knowledge, his power and influence, over and through the laws of nature, he is and can be omnipresent throughout all the works of God. It is not the Holy Ghost who in person lighteth every man who is born into the world, but it is the light of Christ, the Spirit of Truth, which proceeds from the source of intelligence, which permeates all nature, which lighteth every man and fills the immensity of space. You may call it the Spirit of God, you may call it the influence of God’s intelligence, you may call it the substance of his power, no matter what it is called, it is the spirit of intelligence that permeates the universe and gives to the spirits of men understanding, just as Job has said. (Job 32:8; Doc. and Cov. 88:3-13.)
Teachings of the Prophet Joseph Smith, Section Four 1839–42, p.207
In tracing the thing to the foundation, and looking at it philosophically, we shall find a very material difference between the body and the spirit; the body is supposed to be organized matter, and the spirit, by many, is thought to be immaterial, without substance. With this latter statement we should beg leave to differ, and state the spirit is a substance; that it is material, but that it is more pure, elastic and refined matter than the body; that it existed before the body, can exist in the body; and will exist separate from the body, when the body will be mouldering in the dust; and will in the resurrection be again united with it.