Matter is one mode of being; spirit is another mode of being as authentic as matter. Material things have certain characteristics. For instance, they have weight. Everything that is material weighs something; it yields to gravitational pull. Then, matter has dimensions; you can measure the thing if it is made of matter. It has shape. It has an outline of some sort, no matter whether it is a molecule or an atom or whatever it may be, on up to the stars that shine. Then, it is extended in space. So I say that weight, dimension, shape and extension are the things that belong to matter. That is one mode of being; that is one way of existing. One power of spirit, or any spirit (for I am talking about spirit now, not about the Holy Spirit), is its ability to penetrate. Matter bumps against other matter and stops; it cannot penetrate. Spirit can penetrate everything. For instance, your body is made of matter, and yet your spirit has penetrated your body completely. Spirit can penetrate spirit. It can penetrate personality—oh, if God’s people could only learn that spirit can penetrate personality, that your personality is not an impenetrable substance, but can be penetrated. A mind can be penetrated by thought, and the air can be penetrated by light, and material things and mental things, and even spiritual things, can be penetrated by spirit. 

   Now, what is the Holy Spirit? Not who, but what? The answer is that the Holy Spirit is a Being dwelling in another mode of existence. He has not weight, nor measure, nor size, nor any color, no extension in space, but He nevertheless exists as surely as you exist.  

How To Be Filled With The Holy Spirit - A.W. Tozer