War and Peace. Two rivals may sharply distinguish between threatening gestures and a clear attack. They can approach the point of no return many times, as a form of negotiation. But there is a threshold beyond which a fight or a war ensues: throwing the first punch, crossing the Rubicon, invading Poland.
Flirtation and Breaking Up. Two people may approach the point of openly showing romantic interest in each other without crossing that threshold by giving a clear signal of their affection. Likewise, they may display signs of dissatisfaction with their relationship without explicitly showing that they are ready to break up with each other. Their attraction or animosity keep bringing them to the brink, but their hesitation about crossing the line holds them back as they approach it. There are gestures they can make which will cause an acceleration into romance or into social distance. But these moments “on the verge” are fleeting.
Infection. Minor infections can sometimes be cleared up by the innate immune system without triggering an adaptive immune response. Beyond a certain point, immune signaling is sufficient to activate the beginnings of an adaptive response and trigger T cell proliferation.
War and Peace. Two rivals may sharply distinguish between threatening gestures and a clear attack. They can approach the point of no return many times, as a form of negotiation. But there is a threshold beyond which a fight or a war ensues: throwing the first punch, crossing the Rubicon, invading Poland.
Flirtation and Breaking Up. Two people may approach the point of openly showing romantic interest in each other without crossing that threshold by giving a clear signal of their affection. Likewise, they may display signs of dissatisfaction with their relationship without explicitly showing that they are ready to break up with each other. Their attraction or animosity keep bringing them to the brink, but their hesitation about crossing the line holds them back as they approach it. There are gestures they can make which will cause an acceleration into romance or into social distance. But these moments “on the verge” are fleeting.
Infection. Minor infections can sometimes be cleared up by the innate immune system without triggering an adaptive immune response. Beyond a certain point, immune signaling is sufficient to activate the beginnings of an adaptive response and trigger T cell proliferation.