Where it is a duty to worship the sun it is pretty sure to be a crime to examine the laws of heat.

Morley contrasts worship with understanding. If a society makes veneration of a phenomenon (the sun) a civic or religious obligation, then asking analytical questions about it (how heat works) becomes socially dangerous, even criminal. The point generalizes: wherever authority demands reverence, it tends to suppress curiosity, because explanation can demystify what power wants kept unquestioned. The quote therefore defends intellectual liberty and the scientific temper, warning that sacralizing ideas—whether religious, political, or cultural—creates incentives to punish dissent and inquiry. It also implies that genuine respect for truth requires allowing investigation, not enforcing piety.