μὲν [31 verses](partic) "Indeed" is men , which is generally used to express certainty and means "indeed," "certainly," "surely," and "truly." Alone in a question, it assumes the answer like "I take it" or "isn't it."  Used with the conjunction de,  it points out the specific word being contrasted after the conjunction. In English, we usually say, "on one hand...on the other hand." See the article here for specific uses with other particles.  -- The "truly" here is a particle, which, when used alone, expresses certainty, "truly" and "certainly." Alone in a question, it assumes the answer like "I take it" or "isn't it."  However, when used with the conjunction translated here as "but" takes on the meaning "on one hand..." with the "on the other hand" identified by the "but" phrase.