I think you should almost replace "spoken language" in that quote with "natural language". As opposed to a formal syntax like used by Russel and Walllace -- or

I think you should almost replace "spoken language" in that quote with "natural language". As opposed to a formal syntax like used by Russel and Walllace -- or indeed any programming language. I say "almost replace" because even natural languages can be restricted into formal versions good enough for proofs. People have been playing that game since Aristotle and his sylogisms.