He instantly senses their purpose. Hamlet goes on further to say that not even an animal or beast, who has no reasoning skills, would have abandoned the mourning so quickly.
Quote 7 To be, or not to be: that is the question. The words used here in metaphorical sense convey his purpose of attacking his mother on emotional front.
If it be now, 'tis not to come. O, what a rogue and peasant slave am I! Our natural hot blooded reaction is cooled by over-analysing the issue. On the one hand, there is no denying that his advice is often sound, if generally cliched and obvious, and very memorably expressed.
Speaking of his cruel reasoning in this moment, Samuel Johnson wrote, "This speech, in which Hamlet, represented as a virtuous character, is not content with taking blood for blood, but contrives damnation for the man that he would punish, is too horrible to be read or to be uttered.
Hamlet speaks these sarcastic words to Rosencrantz and Guildenstern whom King Claudius has appointed to spy on Hamlet.
Act I, Scene II. If it be not to come, it will be now. A small element of evil can corrupt an otherwise virtuous individual.