Syllogism for SSC GD

A syllogism gives you two or three statements and a few conclusions. You decide which conclusions definitely follow from the statements. Not which are likely, and not which are true in real life. Only which must be true if the statements are true.

That one idea explains most wrong answers. The statements may sound strange ("All chairs are birds"). Accept them anyway. And do not bring in anything you know from outside. If the statements do not force the conclusion, it does not follow.

Syllogism appears in the SSC GD reasoning section, often as two statements with one or two conclusions. With a quick circle drawing it takes under a minute.

Three key words as circles

"Some" means at least one, possibly all. It does not mean "some but not all". Reading it as "not all" is another common source of mistakes.

Which statements can be reversed

"All dogs are animals" does not mean "all animals are dogs". But it does mean "some animals are dogs", because every dog is one of the animals.

The method

1. Draw circles for the first statement.
2. Add the second statement. Draw it in the simplest way the words allow.
3. For each conclusion, ask: is it true in this drawing?
4. Then try to break it. Can you redraw the circles, still obeying both statements, so the conclusion becomes false? If you can, it does not follow.

Solved examples

Example 1. Statements: All dogs are animals. All animals are living things. Conclusions: I. All dogs are living things. II. Some living things are dogs.

1. Dog circle inside Animal, Animal inside Living things.
2. Conclusion I: dogs sit inside living things in every drawing. Follows.
3. Conclusion II: every dog is a living thing, so at least some living things are dogs. Follows.
4. Answer: both I and II follow.

Example 2. Statements: All roses are flowers. Some flowers are red. Conclusion: Some roses are red.

1. Rose inside Flower. Red overlaps Flower.
2. Try to break it: draw Red overlapping only the part of Flower outside Rose. Both statements still hold.
3. Answer: does not follow.

Example 3. Statements: No cat is a dog. All dogs are pets. Conclusions: I. No cat is a pet. II. Some pets are dogs.

1. Dog inside Pet. Cat apart from Dog.
2. Conclusion I: Cat could still overlap the part of Pet outside Dog. Does not follow.
3. Conclusion II: all dogs are pets, so some pets are dogs. Follows.
4. Answer: only II follows.

Example 4. Statements: Some boys are players. All players are fit. Conclusions: I. Some boys are fit. II. All fit people are players.

1. Boys overlap Players. Players inside Fit.
2. Conclusion I: the boys who are players are inside Fit. Follows.
3. Conclusion II: this reverses "all players are fit". Does not follow.
4. Answer: only I follows.

Example 5. Statements: All pens are books. No book is a bag. Conclusions: I. No pen is a bag. II. Some bags are pens.

1. Pen inside Book. Bag apart from Book.
2. Pens are inside books, and books never touch bags. So no pen is a bag. I follows.
3. II contradicts I. Does not follow.
4. Answer: only I follows.

Example 6 (either-or). Statements: Some cups are plates. Some plates are spoons. Conclusions: I. Some cups are spoons. II. No cup is a spoon.

1. Cups overlap Plates, and Plates overlap Spoons. Cups and Spoons may or may not touch.
2. So neither I nor II follows on its own.
3. But I and II are about the same two groups, and between them they cover every case: either some cups are spoons, or none is.
4. Answer: either I or II follows.

Common mistakes

Practice set

1. All boys are students. All students are young. Conclusion: All boys are young.
2. Some pens are blue. All blue things are bright. Conclusion: Some pens are bright.
3. All cars are vehicles. Conclusion: All vehicles are cars.
4. No fish is a bird. Conclusion: No bird is a fish.
5. All teachers are readers. Some readers are singers. Conclusion: Some teachers are singers.
6. All apples are fruits. No fruit is a stone. Conclusion: No apple is a stone.
7. Some chairs are tables. Conclusion: Some tables are chairs.
8. Some books are pens. No pen is red. Conclusions: I. Some books are not red. II. No book is red.

Answers:

1. Follows. Boys inside Students, Students inside Young.
2. Follows. The pens that are blue are inside Bright.
3. Does not follow. Only "some vehicles are cars" follows.
4. Follows. "No" statements reverse.
5. Does not follow. Singers may overlap only the readers who are not teachers.
6. Follows. Apples are inside Fruit, and Fruit never touches Stone.
7. Follows. "Some" statements reverse.
8. Only I follows. The books that are pens are not red. Other books may or may not be red, so II does not follow.

What to do next

• Learn the two tables above: the three circle pictures and which statements reverse.
• Solve 10 syllogism questions a day for a week, drawing circles every time.
• For each conclusion you accept, spend five seconds trying to break it with a different drawing.
• Revise Venn diagrams, which use the same circles with real-world knowledge.