All hummingbirds are richly colored.
No large birds live on honey.
Birds that do not live on honey are dull in color.
All hummingbirds are small.

The following sorites are taken from Lewis Carroll’s Symbolic Logic. All are valid. Rewrite each sorites in standard form, using letters to represent the terms and reducing the number of terms whenever necessary. Then use Venn diagrams or the rules method to prove each one valid.