"physical substance" is term that isn't used in physics, since "substance" is a term used by philosophy. But I think I know what you mean. You need not to believe there is more than "substance", it is something you experience each day and when you say there is more than substance you have all the physicists and almost everybody else by your side. BUT, and this is a huge "but" this that is there beyond "physical substance" is hardly to be separated from "substance". The idea that there are the things that physics is interested in and those in which soulseekers are interested in and that those things are of different kind and exist independently of each other is a concept that does not work. When I have a glas of wine, the wine is a physical substance and we can measure it in many ways and find it's characteristics in order to describe it. But when the glas is broken... it changes the wine in a way. The state of the wine is altered, all the relationships between me and the glass and the wine and the wine in the glass get affected. The wine splashes to the floor, the glass is broken and unusable, the wine still is wine but you cannot drink it with pleasure any more, the taste suffers, the scent is lost, the sparkle of light the wine makes is lost, the dreamy atmosphere is lost and many more things get lost when the wine and the glass and me enter the sad state of the broken glass, the spilled wine. Now replace the complex relationship and state of the wine with the state of existence of any other thing. When you think about it your "physical substance" is merely a thing in a state that you stripped off its relationship with everything and just regard as something existing without all those relationships. But it is the complex sort of relationships of those things that make their soul and meaning? When you pour a shot of whisky in a glass the whisky keeps most of it's properties and gains some new ones and when you smash the glass it changes many of it. When you want to know where the soul is you have to answer the question where the galss of wine is when the glass gets broken. It is state change after all, the state of your physical substance changes while the substance is somehow still there, though in a different form. The physical substance cannot be without a form or state. It always has one, but not always the same and some are ever changing. So yeah, to have a soul or spirit is nothing but the complex state of substances with each other and with all the things around. So yes there is much more than the pure substance, but it isn't exactly a mystery or invisible property, but it is in plain sight though not always visible to the human eye in all its characteristics.