Page 173

Location: Explanation of "The Secret", after Problem 4

It is (top of the page, lines 5-7)

... Therefore \(S(K(SI))\) is a thrush. The reader can check this by computing \(S(K(SI))xy\); he will end up with yx.

It should become

... Therefore \(S(K(SI))K\) is a thrush. The reader can check this by computing \(S(K(SI))Kxy\); he will end up with yx.

Short explanation

The final Kestrel in the expression for \(T\) is needed, indeed:

\[ Txy=S(K(SI))Kxy=K(SI)x(Kx)y= SI(Kx)y=Iy(Kxy)=yx\;. \]