Translating "dukkha" as "reactivity"

As I understand reactivity is incessant and chaotic mind response to external stimuli (through senses ofcourse). But reactivity cannot be called suffering because it is the root cause of suffering. Mind impacts body in a negative way. Mind also impacts emotional health badly. When mind (desire) causes action it is past (I am) or future oriented (I want to be). Certain actions are caused by body e.g. intake of food. Many actions originates in Heart for example a song or a painting. These actions will not be the cause of suffering because you will not loose awareness while performing these actions.

Mind's natural condition is to be silent and work only when needed. Right now a civilized man's mind work all the time for no reason. This 24/7 schedule is the main reason why modern man is an unhappy lot.

I think Brown has gone a bit overboard by defining reactivity as suffering (Dukkha).

When you have contact your consciousness react with some sensation or the other. If the sensation is unpleasant it is unsatisfactory, it is pleasant and changes or ends it is still unsatisfactory and if is neutral it is still unsatisfactory as wholesome and unwholesome roots which create future sensation are still present and the process of rebirth continues. If you crave to any of the sensations then you create suffering for the future, but if you are equanimous the seed of past karma which gave fruit will not find fertile ground to give results in the future. [Cūla Vedalla Sutta]

So your ingrained habitual reaction to contact creates sensation which in turn creates sensation which lead to unsatisfactoriness with the contact and potential to create unsatisfactoriness is the future. [Cūla Vedalla Sutta] If you develop equanimity in the face of pleasant and unpleasant sensations than craving and aversion and wisdom in the face of neutral sensation, than the habitual reaction then you can overcome in contact with sense objects, will prevent future occurrence of unsatisfactoriness. [Pahāna Sutta, Avijja Pahana Sutta 2]

I feel the authors is relating his understanding that the habitual reaction is what keep you rolling in misery in the future and this tendency to react creates misery now, but I feel the rendering is inaccurate as it is explaining causality by equating a result to the case, i.e., if A causes B then A is B, which is not the most right way to understand it. In my point of view "reactivity underlies dukkha" would be a better rendering.

Some of the description above are based on:

• Cūla Vedalla Sutta

pleasant feeling is pleasant when it persists, painful when it changes;

painful feeling is painful when it persists, pleasant when it changes;

neutral feeling is pleasant when there is knowledge of it, painful when there is no knowledge of it

• Pahāna Sutta

the latent tendency of lust should be abandoned in regard to pleasant feeling;

the latent tendency of aversion should be abandoned in regard to painful feeling;

the latent tendency of ignorance should be abandoned in regard to neutral feeling.

• Avijja Pahana Sutta 2

Is there a linguistic or philological basis for translating "dukkha" as "reactivity"?

No I don't think so. Philologically I think of dukkha as being originally an antonym of sukha --

Sukha is a Sanskrit and Pali word that is often translated happiness, ease, pleasure or bliss.

Or is Brown being a bit loose here, reflecting the dynamic that he explains

Yes I think so.

It might make more sense the other way around: to say "reactivity is dukkha" rather than "dukkha is reactivity". Saying "reactivity is dukkha" might not be too surprising, given that everything is dukkha i.e. dukkha is one of the Three marks of existence:

sabbe saṅkhāra dukkhā — "all saṅkhāras are unsatisfactory"

I think that "reactivity" is one example of a saṅkhāra (e.g. "reactivity" a combination of a "reactor" with a "thing-which-it-reacts-to").

'Dukkha' means 'suffering', that is, mental torment, i.e., a lack of peace. So "reactivity" is certain a type of dukkha since reactivity is disturbing, tormenting & not peaceful. However, other mental experiences are also "dukkha", such as sorrow, lamentation, pain, grief & despair. Reactivity or mental concocting is one kind of dukkha (called sankhara-dukkha; see SN 38.14; "stressfulness of fabricating") but it is not a translation of the word "dukkha". "Dukkha" means "difficult to bear"; "hard to endure".