Knights and Knaves Puzzle - Solution

The Puzzle:

Knights and Knaves
There are three people (Alex, Brook and Cody), one of whom is a knight, one a knave, and one a spy.

The knight always tells the truth, the knave always lies, and the spy can either lie or tell the truth.

Alex says: "Cody is a knave."
Brook says: "Alex is a knight."
Cody says: "I am the spy."

Who is the knight, who the knave, and who the spy?

Our Solution:

Alex is a Knight
Brook is a Spy
Cody is a Knave

Brook is not the knight, since if he is, then Alex would also be the knight.
Cody is not the knight, since his statement would then be a lie.

So Alex is the knight. And Cody is the knave, and Brook is the spy.
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