Here are some sample syllogisms to work.  Try them first, and then check your work by clicking here for the solutions.

1. Do a Venn diagram to show whether this syllogism is valid or invalid:

No Merchants are Pirates

Some Sailors are Merchants

Some Sailors aren’t Pirates

2. Using the quality and distribution rules, determine whether the following are valid or invalid.  If invalid, state why.

No Merchants are Pirates

All Sailors are Merchants

Some Sailors are Pirates

All Merchants are Pirates

Some Merchants are Sailors

No Sailors are Pirates

All Pirates are Merchants

No Merchants are Sailors

Some Sailors aren’t Pirates

No Merchants are Pirates

Some Merchants are Sailors

Some Sailors aren’t Pirates

All Merchants are Pirates

All Sailors are Merchants

Some Sailors are Pirates

Some Philosophers are Marines

Some Marines are Salesmen

Some Salesmen are Philosophers

All Marines are Philosophers

All Salesmen are Marines

Some Salesmen are Philosophers

No Philosophers are Marines

Some Marines are Salesmen

Some Salesmen isn’t Philosophers

All Platonists are Medievalists

Some Medievalists aren’t Stoics

Some Stoics aren’t Platonists