Most animals in this zoo are birds.
# Most birds can fly.
# Therefore, most animals in this zoo can fly.

This is fallacious: a zoo could have a large proportion of flightless birds. There is no logical principle that states:

# For some x, P(x).
# For some x, Q(x).
# Therefore, for some x, P(x) and Q(x). An easy way to show the above inference as invalid is by using Euler diagrams. In logical parlance, the inference is invalid, since under at least one interpretation

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