Philosophy · Unit 9

Logic and Arguments

Validity, soundness, deduction, induction and fallacies

Formal logic makes the structure of an argument visible independently of what it is about, which is what allows reasoning to be checked rather than merely felt.

The unit covers validity and soundness, deduction and induction, syllogisms, and the standard fallacies.

This unit breaks down into 23 short steps and 120 questions, starting at difficulty 1 and building to 5. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 23
Questions: 120
Difficulty: 1-5

What this unit covers

Validity
Soundness
Deduction and Induction
Syllogisms
Logical Fallacies

Where this fits

Needs Reasoning and Logic. Underpins the rest of the track.

Where people slip

Naming a fallacy does not refute an argument. Pointing out that someone attacked a person is only decisive if the argument depended on it, and fallacy labels get thrown around far too freely.

How the unit is structured

Logic and Arguments runs as 23 short steps that unlock in order. 17 are practice rounds and 6 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 5 as you progress.

Step 1 · easierStep 23 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

Deduction and Induction

Multiple choiceLevel 1
1. Deductive reasoning aims for conclusions that, if the premises are true, are...
- certaincorrect
- probably right
- popular
- emotional
Good deductive reasoning gives certainty, the conclusion cannot fail if the premises hold.
Fill the blankLevel 2
2. Reasoning that guarantees its conclusion when the premises are true is called ____ reasoning.
- deductivecorrect
- inductive
- emotional
- random
Deductive reasoning is the kind that forces the conclusion when the premises are true.
Sort into groupsLevel 2
3. Sort each piece of reasoning as deductive or inductive.
Answer: All squares have four sides, so this square does = Deductive; Every swan I saw was white, so all swans are white = Inductive; All humans are mortal, so Socrates is mortal = Deductive; It rained last Monday, so it will rain this Monday = Inductive
Deduction guarantees the conclusion from general rules, while induction generalizes from examples.
True or falseLevel 2
4. Inductive reasoning often moves from many specific observations to a general conclusion.
Answer: True
Induction typically gathers particular cases and generalizes, such as noticing many white swans.
Type the answerLevel 2
5. What kind of reasoning generalizes from specific examples to a likely broad conclusion?
Answer: inductive
This is inductive reasoning, moving from particular cases to a general claim.
Odd one outLevel 3
6. Three of these are deductive arguments. Which one is inductive instead?
- Every crow I have seen is black, so all crows are black
- All squares have four sides, so this square has four
- All humans are mortal, so Ada is mortal
- If it is a triangle it has three sides; this is a triangle, so it has three
Generalizing from observed crows to all crows is inductive, while the others guarantee their conclusions.

Logical Fallacies

Multiple choiceLevel 1
7. An ad hominem fallacy attacks...
- the person instead of their argumentcorrect
- the evidence very carefully
- the conclusion logically
- the topic in general
An ad hominem goes after the person making the argument instead of the argument itself.
Choose all that applyLevel 2
8. Which of these are names of logical fallacies?
- Circular reasoningcorrect
- False dilemmacorrect
- Post hoccorrect
- Valid deduction
- Sound argument
Circular reasoning, false dilemma, and post hoc are all named fallacies, while valid deduction and sound argument are not.
Fill the blankLevel 2
9. A false dilemma presents only two choices when in fact ____ options exist.
- morecorrect
- no
- zero
- funny
A false dilemma hides the fact that more than two options are really available.
Match the pairsLevel 2
10. Match each fallacy to what it does.
Answer: Ad hominem = Attacks the person, not the argument; Straw man = Distorts an argument to attack it; False dilemma = Offers only two options when more exist; Slippery slope = Says one small step leads to disaster
Each named fallacy has a distinct trick, from attacking the person to offering only two options.
Odd one outLevel 2
11. Three of these are logical fallacies. Which one is the odd item that is actually good reasoning?
- Weighing relevant evidence carefullycorrect
- Slippery slope
- Straw man
- Ad hominem
Carefully weighing relevant evidence is sound reasoning, while the others are fallacies.
True or falseLevel 2
12. An appeal to authority can be a fallacy when the person cited is not actually an expert on the topic.
Answer: True
Citing an authority is misleading when that person has no real expertise in the matter.

Soundness

Multiple choiceLevel 1
13. A sound argument is one that is valid and also has...
- all true premisescorrect
- a famous author
- exactly three premises
- a surprising conclusion
Soundness adds a requirement to validity, that every premise is actually true.
Choose all that applyLevel 2
14. Which two things must both be true for an argument to be sound?
- It is validcorrect
- All its premises are truecorrect
- It has a famous author
- It has exactly four premises
- Everyone agrees with it
A sound argument is valid in form and has premises that are all actually true.
Fill the blankLevel 2
15. To be sound, an argument must be valid and have premises that are all ____.
- truecorrect
- false
- short
- clever
Soundness requires a valid form together with premises that are actually true.
True or falseLevel 2
16. Every sound argument is also a valid argument.
Answer: True
Soundness is defined as validity plus true premises, so a sound argument is always valid too.
Type the answerLevel 2
17. What word means an argument that is both valid and has all true premises?
Answer: sound
That word is sound, meaning valid plus true premises.
Choose all that applyLevel 3
18. Which of these could stop a valid argument from being sound?
- At least one premise is falsecorrect
- A premise contradicts realitycorrect
- The conclusion is unpopular
- It happens to have two premises
- The author is unknown
Soundness fails whenever a premise is false, no matter how the conclusion sounds or who wrote it.

Syllogisms

Fill the blankLevel 1
19. All men are mortal. Socrates is a man. Therefore Socrates is ____.
- mortalcorrect
- immortal
- a god
- a myth
The two premises force the conclusion that Socrates, being a man, is mortal.
Multiple choiceLevel 1
20. A classic syllogism has two premises and one...
- conclusioncorrect
- question
- fallacy
- author
A syllogism links two premises to reach a single conclusion.
Guess the numberLevel 2
21. How many premises does a classic categorical syllogism have before its conclusion?
Answer: 2
A classic syllogism uses two premises, a major and a minor, to reach one conclusion.
Put in orderLevel 2
22. Put this classic syllogism in the correct order, from first premise to conclusion.
Answer: All men are mortal -> Socrates is a man -> Therefore Socrates is mortal
Two premises come first, then the conclusion that Socrates is mortal follows.
Match the pairsLevel 3
23. Match each part of the classic syllogism to its example.
Answer: Major premise = All men are mortal; Minor premise = Socrates is a man; Conclusion = Socrates is mortal; Middle term = man
The major premise is the general claim, the minor is the specific one, and 'man' is the shared middle term.
Choose all that applyLevel 5
24. Which of these are genuine rules for a valid categorical syllogism?
- The middle term must be distributed at least oncecorrect
- It must contain exactly three termscorrect
- Two negative premises yield no valid conclusioncorrect
- It must contain a fallacy
- The conclusion must be a question
A valid syllogism has exactly three terms, distributes the middle term at least once, and cannot draw a conclusion from two negative premises.

Validity

Multiple choiceLevel 1
25. In logic, an argument is called valid when, if all its premises are true, its conclusion...
- must also be truecorrect
- could still be false
- is only a guess
- depends on who is speaking
Validity means the premises properly force the conclusion, so true premises make the conclusion have to be true.
Fill the blankLevel 2
26. In a valid argument it is impossible for the premises to be true while the conclusion is ____.
- falsecorrect
- true
- long
- kind
A valid form never lets true premises lead to a false conclusion, that is the whole point of validity.
Odd one outLevel 2
27. Three of these describe validity. Which one is the odd statement that has nothing to do with validity?
- How loudly the speaker talkscorrect
- It concerns the argument's form
- True premises would force a true conclusion
- It can hold even with false premises
Validity is about logical form, not how loud or confident the speaker is.
True or falseLevel 2
28. Validity depends on an argument's logical form, not on whether its premises happen to be true in the real world.
Answer: True
Validity is about structure, so a valid argument keeps its shape even if the premises are actually false.
Type the answerLevel 2
29. What one word describes an argument whose form guarantees the conclusion whenever the premises are true?
Answer: valid
This is the word valid, describing an argument whose structure forces the conclusion.
Choose all that applyLevel 3
30. Which statements about validity are correct?
- A valid form guarantees the conclusion if the premises are truecorrect
- Validity depends on the logical structurecorrect
- A valid argument must have true premises
- Validity means the argument is spoken loudly
Validity is about form and guarantees the conclusion from true premises, but it does not require the premises to actually be true.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 10 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Choose all that apply
Fill the blank
Guess the number
Match the pairs
Multiple choice
Odd one out
Put in order
Sort into groups
True or false
Type the answer

Practise Logic and Arguments

120 questions across 23 steps. Start with step one and crawl at your own pace.

Play this unit

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