Reciprocal Mode

The reciprocal mode is perhaps the strangest and most difficult one to understand.

Here is what Sextus says about it:

The reciprocal mode is erected whenever the thing that ought to confirm the matter being investigated needs assurance [pistis] from the thing being

investigated. In this case, since we are not able to accept either of them for the establishment of the other, we suspend judgment about both of them. (PH I 169)²⁸⁴ Most commentators think that Sextus is talking about circular arguments here. There are several difficulties with this suggestion. First, when Sextus describes the mode, he only mentions two things which confirm each other, rather than presenting the more general case of arbitrarily large circular arguments.²⁸⁵ Most scholars suggest that Sextus is

handling the simplest case, but that he would extend it if pressed.²⁸⁶ Second, when Sextus appeals to this mode, sometimes he takes issues with argumentative claims, but often he points out a conceptual rather than a logical interdependence. Assuming that Sextus is using the mode correctly in those circumstances, then the assurance that he speaks of need not be a matter of demonstrative justification or proof.

As I suggested above, on my view, the reciprocal mode is meant to handle a potential grounding scenario, like the mode from relativity and the mode from

284ὁ δὲ διάλληλος τρόπος συνίσταται, ὅταν τὸ ὀφεῖλον τοῦ ζητουμένου πράγματος εἶναι

βεβαιωτικὸν χρείαν ἔχῃ τῆς ἐκ τοῦ ζητουμένου πίστεως· ἔνθα μηδέτερον δυνάμενοι λαβεῖν πρὸς κατασκευὴν θατέρου, περὶ ἀμφοτέρων ἐπέχομεν. (PH I 169)

285This is not just an issue about how Sextus presents the mode, but also about how he uses the mode in his writings. Barnes (1990, 64) notes that Sextus appeals to reciprocity many times, but only ever considers pairs of arguments or definitions. That is, he never considers “circles” larger than two.

286Barnes (1990, 61) says that the reciprocal mode must oppose circular arguments of any size to be perfectly general, but he admits that a) Sextus only appeals to pairs when he evokes the reciprocal mode and b) many of those pairs are not arguments at all. Morison (forthcoming, 18 n10) agrees with Barnes that the reciprocal mode covers circular arguments of any size. Hankinson (1995a, 187) also claims that the mode must be extended to circular arguments of any size in order for the modes to be perfectly general.

hypothesis. Once again, Diogenes Laertius can help us better understand the mode:

But the reciprocal mode is erected whenever the thing which ought to confirm the matter under investigation needs assurance from the thing being investigated, for example, if someone, while he confirms the existence of pores because out-flows happen, should accept this very thing as confirmation that out-flows happen. (DL IX 89)²⁸⁷

The example that Diogenes offers in this case is enlightening. The idea seems to be that the dogmatist in question claims that the existence of pores is both a necessary and sufficient condition for the occurrence of emanations, that is, sweat. On my

interpretation, the skeptics saw this as a dogmatic grounding technique distinct from the hypothetical foundationalism.²⁸⁸ The reciprocal mode should be used when a dogmatist thinks that he can ground the discussion by providing the correct necessary and sufficient conditions for something. The dogmatist might be satisfied that he has provided the correct analysis of pores; moreover, he might claim that he has not simply posited that emanations occur since it is entailed by the existence of pores.

It is true, in a sense, that this is a circular argument, but why would the skeptic suspend judgment on that basis?²⁸⁹ It cannot be that the skeptic believes that a reciprocal argument is non-probative or begs the question, even if it does.²⁹⁰ Morison claims that the

287ὁ δὲ δι' ἀλλήλων τρόπος συνίσταται ὅταν τὸ ὀφεῖλον τοῦ ζητουμένου πράγματος εἶναι βεβαιωτικὸν χρείαν ἔχῃ τῆς ἐκ τοῦ ζητουμένου πίστεως, οἷον εἰ τὸ εἶναι πόρους τις βεβαιῶν διὰ τὸ ἀπορροίας γίνεσθαι, αὐτὸ τοῦτο παραλαμβάνοι πρὸς βεβαίωσιν το<ῦ> ἀπορροίας γίνεσθαι.

(DL IX 89)

288Note the Aristotle at An. Post. I 3 72a18-24 says that immediate syllogistic principles can either be hypotheses OR definitions (horismos). So there is more than one type of grounding principle for scientific explanations even in the case of certain individual dogmatic philosophers, like Aristotle.

289Thorsrud (2009) points out that “the charge of circularity does not necessarily lead by itself to epochē”

(158).

290Barnes (1990) implies that Sextus believes reciprocal arguments to be unsound when he says, “We shall hardly entertain the thought that Sextus might have had no objection to large circles, holding that reciprocal argument was the only unsound form of circular argument” (64). While other interpreters point out the problems with the circular argument, they are less clear that this is meant to be a belief that the skeptic holds. See Hankinson (1995a, 188); Thorsrud (2009, 158).

skeptic will construct an equivalent reciprocal argument for the opposing conclusion:

Any reciprocal argument adduced by the dogmatist for the conclusion P can be matched with a reciprocal argument for the conclusion not-P. After all, if the dogmatist can give grounds for his original conclusion which eventually turn out to rely on the proposition P, then the Sceptic can do the same for the proposition not-P.²⁹¹

But I'm not sure why we should think that the skeptic will be able to do this. Taking Diogenes' example above, the skeptic surely would not try to argue that pores do not exist on the basis there are no out-flows (and vise versa) precisely because the existence of pores was posited to explain the observable fact that we sweat.²⁹² If the skeptic were to offer such an opposing argument, then Morison is correct that the formal features of the opposing arguments would be the same, but the arguments would not appear to be equally weighted to anyone who has observed sweat.

On my interpretation, the reciprocal mode calls for the skeptic to grant the interdependence of the two concepts or the two claims. Then the skeptic can ask of the conjunction why the dogmatist thinks both are true or real. Again, taking Diogenes' example, skeptic might concede that out-flows guarantee the existence of pores, but then ask why she should believe that there are both out-flows and pores. This starts the discussion off again and has the effect of suspending judgment about both of the reciprocal parts, just as Sextus says.

The above reconstruction resembles what Sextus does when he uses the mode in

291Morison (forthcoming, 30).

292Note that Hankinson (1995a, 188) is quite right to point out that it is one thing to observe that moisture forms on our skin and quite another to claim that it flows out of our skin since the latter begs the question for the pore theory. Still there is an observable phenomenon that needs explanation. While there certainly could be opposing theories about sweat, a theory could not claim that we do not sweat, and be equally weighted with the phenomena without some compelling argumentation.

his argumentation. So, for example, when he argues against causation, he points out that we do not conceive of cause and effect independently. Rather, we conceive of the cause as the cause of the effect if and only if we conceive of the effect as the effect of the cause.

This raises the reciprocal mode which “shows them both unthinkable or inconceivable”

(PH III 22). The reason he gives is that since each of them needs assurance [pistis] from the other, we will not be have a place from which we will begin to form the concept [ennoia] of them.²⁹³

Similarly, we see Sextus invoke the reciprocal mode in arguments that mirror the Meno paradox. For example, when dogmatists argue that skeptics cannot investigate philosophical doctrines because they do not claim to apprehend anything, Sextus counters with an argument that relies on the relative priority of apprehension and investigation. “If someone wants to begin from apprehension, we divert him to the need to investigate before apprehending, and if he wants to begin from investigation, we divert him to the need to apprehend before investigating that which will be investigated” (PH II 9). Notice that Sextus paints a picture of the argumentative setting by using the first person here.

The idea is that once the skeptic recognizes that the dogmatist has taken a stand (in this example, the claim “skeptics cannot investigate” is supported by the claim that

apprehension of a subject is both necessary and sufficient for its investigation). The skeptic grants the reciprocal claim for the purpose of the argument and then wonders why we should think that apprehension and investigation exist at all since their

293Note the way the language of PH III 22 mirrors the language that Sextus uses for the infinite regress at PH I 166. If my interpretation of the regressive mode is correct, this suggests that the reciprocal mode involves the skeptic requesting support from the dogmatist for the conceptual analysis.

interdependence means that neither gets off the ground. Just as in the case of cause and effect, the claim of interdependence gives the skeptic the opportunity to grant the

dogmatic claim, but then push the question back further. If one cannot be defined without the other, what reason can the dogmatist give to suggest that either concept obtains?