This is a departure from the conventional perception that there is (almost) a linear correlation between the level of external stimulus and satisfaction: external stimulus (brought by products/services etc.) that generate less pain and more pleasure always result in higher satisfaction.
This perspective changes when arousal is plugged in to the equation. Arousal is a bell curve. An assumption can be made that the marginal satisfaction from the change in pain/pleasure level would start diminishing once it hits the plateau of arousal, and starts moving toward boredom or stress.
Interaction of External Stimulus and Arousal
But where does the level of external stimulus meet optimum arousal level? How can we find where the optimal point is?
This is where “zero” comes into play.
Make an assumption for now, that the current level of pleasure for you is too much and is not aligned with an optimal arousal level. You can think of a situation where you got a promotion you desperately wanted, but are made to work for long hours, day after day because of it. Or you’ve gained unwanted weight, developed cavities and became diabetic by eating too many of your favorite sweets. (For the sake of simplicity, we will focus on pleasure, not pain, from this point on.)
Since the assumption is that “too much” pleasure is not desirable, theoretically you can simply start reducing the amount of external stimulus you receive, until you find the right point where it crosses the optimal level of arousal.
If you keep subtracting the amount of pleasure, the pleasure will eventually become zero. “Zero” is the ultimate form of subtraction.
Zero sets a boundary for this experiment: if we keep reducing pleasure towards zero, what will happen to our body and mind? Will we only feel stress or anxiety? Or will something else emerge?