Segal's law is an adage that states:
"A man with a watch knows what time it is. A man with two watches is never sure."
The mood of the saying is ironic. While at a surface level it appears to be advocating the simplicity and self-consistency obtained by relying on information from only a single source, the underlying message is to gently question and make fun of such apparent certainty – a man with one watch can't really be sure he knows the right time, he merely has no way to identify error or uncertainty.
Nevertheless, the saying is also used in its purely surface sense, to caution against the potential pitfalls of having too much potentially conflicting information when making a decision