An example of a universal non-substance is science. Science is present in a subject, the soul, and is said of a subject, grammar. If science was not said of any subject, that would mean that science would be a particular, meaning that science would be contained in another category. Observation reveals the opposite: science is characterized as the study of the natural world through experiments and observation. Thus the particular sciences of Biology, Chemistry, or Astronomy are all categorized in the definition of science and as a result science is defined as a universal because it groups particulars. Additionally, if science was not present in a subject, that would mean that it would be a substance and that science is visible to the senses. This is impossible because science is a study, which is an act of the intellect; something which cannot be seen or felt, existing only in the mind. Thus, universal non-substances are things that are both said of a subject and present in a