If you're really interested in the foundations of filing a counterclaim, I would suggest Brian Blum's seminal work[0]. It will explain in great detail more than I could summarize.
However, I'll relay a parable told to me in first-year law school contracts class:
A man picks up a hitchiker on the side of the road. beautiful girl. She offers to fool around with him while driving (use your imagination). after the act is over, she says "I forgot to mention: I'm a prostitute, and that act cost $50."
Without missing a beat, the driver responds, "It just so happens that I forgot to mention: I'm a taxi driver, and this trip costs $60, so I'll take the $10 you owe me now."
However, I'll relay a parable told to me in first-year law school contracts class:
A man picks up a hitchiker on the side of the road. beautiful girl. She offers to fool around with him while driving (use your imagination). after the act is over, she says "I forgot to mention: I'm a prostitute, and that act cost $50."
Without missing a beat, the driver responds, "It just so happens that I forgot to mention: I'm a taxi driver, and this trip costs $60, so I'll take the $10 you owe me now."
0. https://www.amazon.com/Examples-Explanations-Contracts-Brian...