The source's example first takes the connection “If something is human, it is an animal”, and then connects it to “If it is not an animal, it is not human.”
The full structure is “If the first conditional connection holds, the second conditional connection holds.” Thus the outer proposition is connected, while its antecedent is connected and its consequent is also connected.
One conditional can be a component of another. The inner “if” and the outer “if” perform different structural roles.
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The Two Sides of Conditionals: Composite Antecedents and Consequents
The source's example first takes the connection “If something is human, it is an animal”, and then connects it to “If it is not an animal, it is not human.”
The full structure is “If the first conditional connection holds, the second conditional connection holds.” Thus the outer proposition is connected, while its antecedent is connected and its consequent is also connected.
One conditional can be a component of another. The inner “if” and the outer “if” perform different structural roles.