H. P. GRICE (M. A. LIT. HUM.) E LA STORIA DELLA FILOSOFIA ROMANA ANTICA

Usener’s influence is also the cause of a fatal blind spot in Diels. 

He failed to acknowledge that Theophrastus, too, had a sort of Doktorvater, namely Aristotle. 

Aristotle, in his treatises, as a rule lists and discusses the opinions (doxai) of men in general and of the experts (who often are philosophers) in particular, concerning an issue in metaphysics, or physics, or psychology, and sometimes ethics, before embarking on his own investigations. 

These opinions are ordered according to the method of diaeresis, or division: a classification according to sets, sub-sets and sub-sub-sets with specific differences. 

Aristotle checks to what extent these opinions are in agreement among themselves or contradict each other, and then tries to establish to what extent one of the available options may prove acceptable, at least as the starting-point for further inquiry, or whether some option may be available which others have failed to consider. 

We call these exegetical and evaluative overviews ‘dialectical’, in the Aristotelian sense of the word of course. 

An overview of this nature should establish which genus, or set, is at issue, that is to say whether we are faced with a theoretical discipline, such as physics (and then with what species, or sub-set, e.g., zoology), or with a non-theoretical discipline such as poetics. 

This approach should also be applied to the sub-sets, or particular objects of inquiry, embraced by a particular sub-set. 

According to Posterior Analytics 2.1 various aspects should (or may) be treated separately, viz.: (1) does the object of the inquiry possess a particular property or attribute, or not; (2) the reason why it does possess this attribute; (3) the existence or non-existence of the object (for instance: do gods exist?—a question one does not need to ask when humans, or the sun, are at issue); and (4), the substance or definition of the object. 

Here an important part is played by the Aristotelian so-called categories and other kinds of predicates, because it is of major importance to establish to what category (viz. substance, or quality, or quantity, or place, or doing and being-affected etc.) a given object of inquiry and/or its attributes belong, or whether and in what sense for instance motion (or rest) may be predicated of it. 

These four different primary questions, or types of questions, may moreover be formulated in respect of each category (viz., not only of substance, but also of quality, etc.). 

Take the objects of mathematics. 

According to Aristotle these do not belong to the category of substance but to that of quantity. 

But within this latter category one may formulate questions about properties, or attributes, which may belong to them; enquire whether they exist, and if so, in what way; ask whether they move or not; and so on.  

In his treatise on dialectic and its methods, the Topics (1.14), Aristotle provides instructions on how to select and classify propositions (protaseis) and problems (problêmata).

We should also make selections from the literature and include these in separate lists for each set, with separate headings, for instance ‘On the Good’, or ‘On the Living Being’—that is to say the Good as a whole, starting with (the question) ‘what is it?’ 

One should cite the doxai [opinions, tenets] of individual thinkers, e.g., that Empedocles said that the elements of bodies are four in number […].  

Of propositions and problems there are — to comprehend the matter in outline — three sets: some are ethical, others physical, others again logical. 

Ethical: for instance (the problem) whether one should obey one’s parents or the law, when these disagree with each other. 

Logical: for instance (the problem) whether the knowledge of opposites is the same, or not. 

Physical: for instance (the problem) whether the cosmos is eternal or not.  

Consequently, propositions and problems can be, and therefore in some cases should be, elucidated by means of tenets, or opinions: doxai. 

As there are three sets of propositions, so there are three sets of doxai: physical, ethical, and ‘logical’ (i.e., general). 

An example of such a diaeresis, or division, of a sub-set which is of fundamental importance for Aristotle is found at the beginning of his Physics. 

This division pertains to two categories and one predicate of a different sort: the number (category of quantity), nature (category of substance) and motion vs. rest (category of doing and being-affected) of the principles (archai) and elements (stoicheia) posited by Aristotle’s predecessors in the field of natural philosophy. 

In line with the rule formulated in the Topics names of philosophers are added to some of the doxai. 

Numerous other examples of this ingredient of the dialectical method are to be found in Aristotle’s writings.  

The above-cited passage from the Topics, and Aristotle’s general practice, help to determine and explain the title of the Theophrastean treatise Diels believed to be foundational: it should be Physikai Doxai, i.e., ‘Tenets in [the various fields of] Natural Philosophy’. 

And one of the rare extant fragments of this treatise not only proves (because of the formulation in Greek of the title as quoted) that this title really is ‘Physical Tenets’, but also demonstrates that such tenets were criticized according to the rules of dialectic. 

Theophrastus, we are informed, cited a tenet of Plato’s and then formulated ‘the objections’ against it. 

The Greek word for ‘objections’ found in this fragment, enstaseis, is a technical term in Aristotle’s Topics. 

Physical tenets are tenets, or theses, in the fields of natural philosophy in the largest sense, ranging from the principles, via cosmology, astronomy and meteorology etc., to human psychology (including philosophy of mind), biology, and even nosology or the theory of diseases. 

Physical tenets are not only formulated by physikoi, natural philosophers, but also by physicians and astronomers. Aëtius indeed contains a number of medical[4] and astronomical doxai, the oldest of which may derive from sources that can perhaps be attributed to some of Aristotle’s collaborators. 

(For further reading on this topic, see Mansfeld 1990, 1992, 1998, 2016a, Mansfeld & Runia 1997, Runia 1999a, Runia 2004, with criticism in Zhmud 2001 and rejoinder in Mansfeld 2002.)