 As noted above, according to the Scholastics, species and genera are created by nature; every natural substance is a combination of matter and substantial form. The substantial form of any substance is its species essence, which is an immaterial entity that makes the object what it is, makes it a member of a particular species and genus and causes its characteristic properties. So, for the Scholastics, all natural substances belong to a determinate species by nature, independently of any human naming activities. On this view then, if we know what qualities a substance possesses, and we know that all qualities are produced by a substantial form, then it is a simple matter to determine its species simply by noting the qualities the substance exhibits. For example, if what makes a particular object a piece of gold is the possession of the substantial form of gold, then whatever exhibits the properties of gold has the substantial form of gold, and so we know the species to which it belongs is gold. Creating a taxonomy for the Scholastics is attempting to discover how nature has already classified substances into species and genera by looking for similarities among their persistent qualities (qualities that tend to remain even when the circumstances or conditions of the object change) that reveal the deeper similarity of sharing substantial forms.