Stanley E. Porter and Matthew Brook O’Donnell 26 the positive or negative features of the network do not seem to be of importance, and such semantic labelling is found in a variety of networks. A second major question to ask is with regard to the implications of the distribution of system 2 and the aorist tense-form. The question is whether the equiprobable distribution indicates that the aorist is not unmarked. There has probably been too much loose use of language with regard to the so-called unmarked character of the aorist. The equiproba- ble distribution indicates, as predicted, that the forms grammaticalizing the +perfective semantic feature are not in privative opposition to those that are –perfective, but that they are equipollent. In this sense, the aorist tense-form is not unmarked. However, on the basis of a number of other factors, such as morphology, implication and semantics, as well as the pat- terns of distribution when one differentiates the aorist from the present and from the perfect tense-forms, it is accurate to say that the aorist is probably the least heavily marked of those forms 85. b. Patterns of Distribution The probabilistic studies that have been performed also allow for a test- ing of several particular dimensions of verbal aspectual usage. In Verbal Aspect, Porter defined verbal aspect in the following way: «Greek verbal aspect is a synthetic semantic category (realized in the forms of verbs) used of meaningful oppositions in a network of tense systems to gram- maticalize the author’s reasoned subjective choice of conception of a pro- cess» 86. This definition was refined further in Idioms of the Greek New Testament as follows: «verbal aspect is defined as a semantic (meaning) category by which a speaker or writer grammaticalizes (i.e. represents a meaning by choice of a word-form) a perspective on an action by the selection of a particular tense-form in the verbal system» 87. There have been two major objections raised against these definitions 88. One of these revolves around the issue of lexis 89. This response takes several different 85 See Porter, Verbal Aspect, pp. 89-90. 86 Porter, Verbal Aspect, p. 88. 87 Porter, Idioms of the Greek New Testament, pp. 20-21. 88 Objections based upon simplistic or traditional temporal conceptions of the verb are not considered here, since they have already been adequately dealt with in Porter, Verbal Aspect, passim. 89 The major proponents of this position with regard to the Greek of the New Testament are J. Mateos, El Aspecto Verbal en el Nuevo Testamento (Estudios de Nuevo Testamento, 1; Madrid: Ediciones Cristiandad, 1977); cf. idem, Metodo de Analisis Semantico Aplicado al Griego del Nuevo Testamento (Estudios de Filología Neotestamentaria, 1; Córdoba: Ediciones el Almendro, 1989); and S.M. Baugh, «An Introduction to Greek Verbal Aspect in the Non-Indicative Moods» (unpublished manuscript; Westminster Theological Seminary in California, 1995). These categories are not absolute, and several of those listed here could be placed in the next category, with some of those below placed here as well.