Minor: All pens are writing instruments.
Major: Some writing instruments are blue.
Invalid conclusion: Some pens are blue.
The blue writing instruments mentioned in the major might all be instruments of some other kind. Nothing guarantees that any blue one is a pen.
The minor is universal affirmative, but the major is particular affirmative. Meeting only one of the two conditions does not make a productive first-figure argument.
Opening interactive controls...
The First Figure: Conditions of Validity and Four Productive Moods
Minor: All pens are writing instruments.
Major: Some writing instruments are blue.
Invalid conclusion: Some pens are blue.
The blue writing instruments mentioned in the major might all be instruments of some other kind. Nothing guarantees that any blue one is a pen.
The minor is universal affirmative, but the major is particular affirmative. Meeting only one of the two conditions does not make a productive first-figure argument.