"extinct in both..."
See in text (Act I - Scene III)
In Polonius' eyes, Hamlet's love for Ophelia will undoubtedly fade, rendering it dead ("extinct") on arrival, having no real aim or intent other than to distract the Prince from his ruminations. His metaphor about light and heat builds on the notion of passion as a fire or flame and suggests that if Ophelia gets too close to it, she will discover that it is more flashy than substantial.
Sinead, Owl Eyes Contributor
