 Again, the first premise seems to have several parts, each of which is a part of the second premise or the conclusion. (In English, the indefinite article in ‘Every senator is a politician’ cannot be omitted; likewise for ‘Every politician is a liar’. But at least for now, let’s assume that in examples like these, ‘a’ does not itself indicate a propositional constituent.)  Aristotle,  predating the Stoics, noted that conditional claims like the following are sure to be true: if (the property of) being a politician belongs to every senator, and being deceitful belongs to every politician, then being deceitful belongs to every senator. Correspondingly, the inference pattern below is valid.