(which he would sometimes spell as "semeiotic") as the "quasi-necessary, or formal doctrine of signs," which abstracts "what must be the characters of all signs used by…an intelligence capable of learning by experience," and which is philosophical logic pursued in terms of signs and sign processes. Peirce's perspective is considered as philosophical logic studied in terms of signs that are not always linguistic or artificial, and sign processes, modes of inference, and the inquiry process in general. The Peircean semiotic addresses not only the external communication mechanism, as per Saussure, but the internal representation machine, investigating sign processes, and modes of inference, as well as the whole inquiry process in general. Peircean semiotic is triadic, including sign, object, interpretant, as opposed to the dyadic Saussurian tradition (signifier, signified). Peircean semiotics further subdivides each of the three triadic elements into three sub-types, positing the existence of signs that are symbols; semblances ("icons"); and "indices," i.e., signs that are such through a factual connection to their objects. Peircean scholar and editor Max H. Fisch (1978) would claim that "semeiotic" was Peirce's own preferred rendering of Locke's σημιωτική. Charles W. Morris followed Peirce in using the term "semiotic" and in extending the discipline beyond human communication to animal learning and use of signals. While the Saussurean semiotic is dyadic (sign/syntax, signal/semantics), the Peircean semiotic is triadic (sign, object, interpretant), being conceived as philosophical logic studied in terms of signs that are not always linguistic or artificial. Peirce's list of categories Peirce would aim to base his new list directly upon experience precisely as constituted by action of signs, in contrast with the list of Aristotle's categories which aimed to articulate within experience the dimension of being that is independent of experience and knowable as such, through human understanding. The estimative powers of animals interpret the environment as sensed to form a "meaningful world" of objects, but the objects of this world (or "Umwelt", in Jakob von Uexküll's term) consist exclusively of objects related to the animal as desirable (+), undesirable (–), or "safe to ignore" (0). In contrast to this, human understanding adds to the animal "Umwelt" a relation of self-identity within objects which transforms objects experienced into things as well as +, –, 0 objects. Thus, the generically animal objective world as "Umwelt", becomes a species-specifically human objective world or "Lebenswelt" (life-world), wherein linguistic communication, rooted in the biologically underdetermined "Innenwelt" (inner-world)