What is the origin of the idiom "on the face of it" and when to use it?

The idiom "on the face of it" originated from the notion of evaluating or judging something based on its surface appearance or initial impression. It implies that the observed or apparent characteristics suggest a particular understanding or conclusion, but further examination or consideration may reveal a different or more complex reality. The phrase emphasizes the need to delve deeper or look beyond the superficial aspects to obtain a more accurate understanding or assessment of a situation or subject.