Preserving the spirit of Spencer's teaching we must regard all modes of relatedness which are disclosed by scientific research as part and parcel of the constitution of nature, from whatever Source, knowable or unknowable, that constitution be derived. Of these modes there are many; indeed, if we deal with all concrete cases, their number is legion. For purposes of illustration, however, we may reduce them, rather drastically, to three main types. There are relations of the physico-chemical type,[53] which we may provisionally follow Spencer in regarding as ubiquitous; there are those of the vital type, which are restricted to living organisms; there are those of the cognitive type, which seem to be much more narrowly restricted. How we deal with these is of crucial importance. Denoting them by the letters A, B, C we find that there are progressively ascending modes of relatedness within any given type. There is evolution within each type. Within the physico-chemical type A, for example, atoms, molecules, and synthetic groups of molecules follow in logical order of evolution. Now the successive products, in which this physico-chemical type of relatedness obtains, have certain _new and distinctive properties_ which are not merely the algebraic sum of the properties of the component things prior to synthesis. We may speak of them as constitutive of the products in a higher stage of relatedness, thus distinguishing constitutive from additive properties.[54] Similarly when B, the vital relations, are evolved, the living products, in which these specific relations obtain, have new constitutive properties, on the importance of which vitalists are right in insisting, though I emphatically dissent from some of the conclusions they draw from their presence. For if, beyond the physico-chemical, a special agency be invoked to account for the presence of new constitutive properties, then, in the name of logical consistency, let us invoke special agencies to account for the constitutive properties within the physico-chemical--for radio-active properties for example. If a Source of phenomena be postulated, why not postulate One Source of all phenomena from the very meanest to the very highest? There remains the case of C--the synthetic whole in which cognitive relatedness obtains. This is unquestionably more difficult of scientific interpretation. But I believe that like statements may be made in this case also. What we have, I conceive, is just a new and higher type of relatedness with specific characters of its own. But of this more in the sequel.