But what is most interesting in the study of spirit and matter is the nature of vacuum and substance. Substance has a tendency to add substance to itself and to turn all that it attracts into the same substance, and vacuum has a tendency to make a greater vacuum. This shows that there is a continual struggle between substance and vacuum. Where vacuum can get hold of substance it will turn the substance into vacuum, and where substance is stronger it will turn out vacuum and make substance. The idea behind this is not what we might think.