Yōga Sūtras
Yōga Sūtra 1.09
शब्दज्ञानानुपाती वस्तुशून्यो विकल्पः।
Vikalpa is inferred knowledge through words in the absence of actual object.
When we hear a story or watch a movie we imagine the sequence of events taking place in front of us, though in reality neither object exists nor events happen.