Here Bruno suggests two principles for the classification and systematising of the sciences, to which it would have been well had he himself and his successors faithfully adhered. The one is, that the modes of measurement, _i.e._ the methods and laws of the sciences, must differ for the different kinds of existence studied: that a biological law, for example, cannot be adopted as an explanation of mental phenomena, nor the atomic theory account for the phenomena of life. On the other hand there are _orders_ of existence, according to the complexity of the subjects involved. If we regard the science which deals with the more concrete subject as "higher," then each higher science (_e.g._ psychology) must take for granted the principles and results of each lower science (biology, physics, mathematics),--each must adopt and retain a unit for itself, which it has not further to analyse. [Sidenote: The "minima" in the classification of sciences.] In the same way the minima offer a ground for the distinction of the more abstract sciences one from another. The term "individual nature" (_atoma natura_) may, according to Bruno, have one of several uses. It may be applied either "negatively or privatively, and if negatively, then either accidentally or substantially." His instance of the _accidental_ use is a voice or sound, which expands spherically, is wholly wherever it is, _i.e._ the full content of the sound is heard, wherever its influence extends, not a part here, a part there, although the intensity may vary in degree. Of the _substantial_ use examples are the spirit, which is wholly in the whole body of man, or that spirit which is in the whole extent of the life of the earth, by whose life we live and in which we have our being, or, above this substantial nature or individual soul, that of the universe, and supreme above all, the mind of minds, God, one spirit completely filling all things.[396] The atom-nature is _privatively_ so-called, when it is the element and substance of a magnitude which is the same in kind with it, and may be reduced to it, and it is distinguished from the atom _negatively_ so-called, because it is not divisible, either in genus or in species, either _per se_ or _per accidens_. Examples are, (1) in discrete quantities:--unity to the mathematician, the universal proposition to the logician, the syllable to the grammarian; and (2) in continuous quantities, varying with the species of continuum:--the minimal pain, sweetness, colour, light, triangle, circle, straight line, curve; in duration, the instant; in place, the minimal space; in length and breadth, the point; in body, the least and first body. [Sidenote: Minimum as substance.]