In DN 15:28.7 = MN 74:10.1 we find the following argument.
At a time when you feel a pleasant feeling, you don’t feel a painful or neutral feeling; you only feel a pleasant feeling. At a time when you feel a painful feeling, you don’t feel a pleasant or neutral feeling; you only feel a painful feeling. At a time when you feel a neutral feeling, you don’t feel a pleasant or painful feeling; you only feel a neutral feeling.
The idea that only one kind of feeling can be experienced at a time became an oft-repeated adage of Buddhist psychology, but it is not empirically obvious that it is the case. One can, for example, enjoy the taste of cake while feeling guilty about eating it; or experience meditative bliss while also feeling sharp back pain. In fact it seems to me that it’s usually the case that we experience a mix of feelings, and only in exceptional moments is it all pain or all pleasure.
How is it that the suttas teach something that seems so disconnected from experience?
This is usually explained with the theory of momentariness: each occurrence of feeling lasts but a moment, so when we seem to be experiencing a mix of feelings, it is really a rapid oscillation between different types.
The problem with this explanation is that there is no theory of momentariness in the suttas. Perhaps it could be argued that this passage suggests that such a theory is implied. The problem then is the context: this argument is only presented twice, and in both times as part of an argument with a non-Buddhist (in MN 74 this is Dīghanakha, and in DN 15 it is a hypothetical). Even if it were the case that the Abhidhammic system of mind moments were current in the suttas, it is unreasonable to suppose that non-Buddhists were familiar with it or accepted it.
Moreover, the commentaries to these two passages say nothing about momentariness, and don’t really seem to recognize the problem. Bhikkhu Bodhi doesn’t comment on this issue in his translations, and in fact I can’t find anywhere that discusses the problem.
On the contrary, the Buddha’s method of argument was to start with something that was easily apparent so that they would have a shared basis with the person they are discussing with. Thus he begins by establishing that there are three feelings. These are things that are readily apparent in experience.
If we think of the mind in a modern sense, as being correlated with a complex network of interrelated brain functions, it is easy to imagine that there are multiple conflicting feelings. The brain is not instantaneous; it takes time for things to propagate, and many different things are going on at the same time. And it seems to me that the mind is the same: feelings are a complex web.
Might it be a sectarian argument? Analayo says that of the parallels to MN 74, SA 969 says nothing of exclusiveness and instead points to the conditionality of feelings. However, versions found in the Tibetan Pravajravastu and Sanskrit and Tibetan versions of the Avadānaśātaka agree with the Pali in talking of exclusiveness. It’s notable that these are later texts. I can’t find a relevant study of DN 15, but a cursory glance at the Chinese parallels suggests that at least some of them have the exclusivity argument.
If it is a later insertion, then, it seems to be a widespread one which represents an understanding of feelings that is broader than just one school.
It all leaves me feeling rather uneasy—how can such a basic teaching be so in conflict with experience? But at the same time, kind of excited—perhaps the apparent conflict might lead to a deeper understanding. I just seem to have all of these feelings going on at the same time!
Is there a way of understanding that resolves this issue? It will have to be one that does not depend on Abhidhamma or on any subtle philosophy or psychology. It has to be something that is obvious enough to serve as an axiom in an argument with someone who is not a Buddhist. And I have to admit, I can’t see it.