"Science is his forte, and omniscience his foible"

This quote by Sydney Smith is referring to someone who is extremely knowledgeable in the field of science, but who also has a tendency to think they know whatever. The phrase "science is his forte" suggests that this person is especially experienced in the field of science, while the phrase "omniscience his characteristic" suggests that they have a tendency to think they know everything. This could be interpreted as a warning versus the dangers of hubris, or excessive pride. It recommends that while it is essential to be educated and proficient in a particular field, it is likewise crucial to bear in mind that no one can understand everything. This quote is a reminder to remain simple and to recognize that there is always more to discover.