FBI Special Agent Phase I & II Exams Phase I — Logic-Based Reasoning Syllabus

What is the post hoc fallacy?

Post hoc ergo propter hoc: assuming that because one event followed another, the first caused the second — confusing correlation/sequence with causation.

What is a categorical syllogism?

A deductive argument with two premises and a conclusion, each relating two categories using quantifiers (all, some, none), sharing a middle term.

What does the quantifier 'all' assert and how is it diagrammed?

'All A are B' asserts every member of A is inside B. It is diagrammed as A being a subset entirely within B (A→B).

What does the quantifier 'some' assert?

'Some A are B' asserts that at least one A is also a B. It does NOT imply all, and 'some are' does not imply 'some are not.'

What does the quantifier 'no/none' assert?

'No A are B' asserts that the categories A and B share no members — they are completely separate sets.

What is the valid inference from 'All A are B' and 'All B are C'?

Therefore all A are C. This is a valid categorical chain (transitivity of universal affirmatives).

Why is 'All A are B; some B are C; therefore some A are C' invalid?

The 'some B that are C' might be entirely outside A. The premises don't force any A to overlap with C, so the conclusion isn't guaranteed.

What is the contrapositive of 'If A then B'?

'If not B then not A.' The contrapositive is logically equivalent to the original conditional and is always valid.

What is the converse of 'If A then B,' and is it valid?

The converse is 'If B then A.' It is NOT logically equivalent to the original and assuming it is commits a logical error.

What is the inverse of 'If A then B,' and is it valid?

The inverse is 'If not A then not B.' It is NOT equivalent to the original; assuming it commits the fallacy of denying the antecedent.

How do you chain conditionals 'If A then B' and 'If B then C'?

You can validly conclude 'If A then C' (hypothetical syllogism), and its contrapositive 'If not C then not A.'

In logic puzzles, what is the difference between 'must be true' and 'could be true'?

'Must be true' holds in every valid arrangement allowed by the rules; 'could be true' holds in at least one valid arrangement. A 'could be' answer is wrong if it's true in only some scenarios when 'must' is required.

How do you test whether a statement 'must be true'?

Try to construct a single valid scenario where it is false. If you can find even one, it does not 'must be true' — it only 'could be true.'

What does it mean for an answer to 'overreach the stated premises'?

The answer asserts more than the premises support — adding strength, scope, or claims not actually established. Such answers should be eliminated.

What is a quick strategy for eliminating overreaching answers?

Watch for extreme/absolute words (all, never, always, only, must) that the premises don't justify; prefer measured answers that stay within what was stated.

How should you approach an ordering/sequencing puzzle?

Build a single line of slots, place fixed clues first, convert relative clues (before/after) into chains, and track which positions remain open for each element.

How do you diagram a 'before/after' constraint in a sequencing puzzle?

Write it as a relation like X — Y (X earlier than Y). Combine multiple to form chains, but don't assume adjacency unless stated.

What does 'X is immediately before Y' add beyond 'X is before Y'?

It forces adjacency — X and Y occupy consecutive slots with nothing between them, a stronger constraint than mere ordering.

How do you handle grouping/matching constraints?

Set up a grid or columns for the groups, place definite assignments, then apply rules linking elements (together/apart) to fill or block cells.

How do you diagram an 'if-then' rule quickly in a logic game?

Write the trigger → result, then immediately note the contrapositive (not result → not trigger) so you can apply the rule in both directions.

How do you diagram an inclusive 'either/or' constraint?

'Either A or B' means at least one is present: not A → B, and not B → A. Inclusive 'or' allows both unless the puzzle says otherwise.

How is an exclusive 'or' different from inclusive 'or'?

Exclusive or means exactly one (not both); inclusive or means at least one (possibly both). Logic problems default to inclusive unless stated as exclusive.

How do you identify the main claim (conclusion) in a reading-based argument?

Ask 'What is the author ultimately trying to convince me of?' The main claim is supported by the other statements but supports nothing above it.

What distinguishes supporting evidence from the main claim?

Supporting evidence (facts, examples, data) is offered TO back the main claim; the main claim is the point those pieces lead toward.

What does a 'strengthen' question ask you to do?

Find the answer that adds support to the argument's conclusion or makes its assumption more likely true.

What does a 'weaken' question ask you to do?

Find the answer that undermines the conclusion — often by attacking the key assumption, offering an alternative explanation, or supplying a counterexample.

What is an 'assumption' question testing?

It asks for an unstated premise the argument depends on — something that must be true for the conclusion to follow from the premises.

What is the negation test for assumption questions?

Negate the candidate assumption; if the argument falls apart, it was a necessary assumption. If the argument survives, it wasn't required.

What is the difference between an inference question and an explicit-detail question?

An explicit-detail question is answered by something directly stated in the text; an inference question requires a conclusion that must be true based on the text but isn't stated outright.

In inference questions, why prefer the 'weakest' supportable answer?

Inference answers must be guaranteed by the text. Cautious, modest statements are easier to support; strong/extreme claims usually overreach and are traps.

What is a 'scope shift' trap answer?

An answer that subtly changes the topic, range, or terms of the argument — addressing something broader, narrower, or different from what the premises covered.

What is a 'reversed logic' trap answer?

An answer that swaps the direction of a relationship — e.g., treating the converse as equivalent, or flipping cause and effect, or necessary and sufficient conditions.