Amphiboly is syntactic ambiguity. "The foolish fear that God is dead." This sentence is amphibolous because its ambiguity does not have a semantic origin in the multiplicity of meaning of any constituent word, but derives from the ambiguous way the words are put together. On one reading, the construction is a sentence: 'The foolish/ fear that God is dead.' On the other reading, it is not a sentence, does not express a compete thought, but is a sentence-fragment: ' The foolish fear/that God is dead.'
A good writer avoids ambiguity except when he intends it.