 This completes the proof of the knowability of \(\lambda\), corresponding to the informal argument that \(KS\) is known by some agent. Note the similarity between the two pieces of proof in lines 1–7 and 8–14. The only difference is that in the latter all formulae are preceded by an extra K. This is because lines 8–14 express the same line of reasoning as lines 1–7 with the only difference that the latter is a proof of the knowability of \(\lambda\) rather than the truth of \(\lambda\). Having concluded that \(\lambda\) is both true and knowable, we now immediately obtain a contradiction as in the paradox of the knower: