This is an explanation of the second logic game from Section III of LSAT preptest 67, the October 2012 LSAT.

Seven professors are giving guest lectures in a literary theory course. The seven professors are Powell, Shihab, Taylor, Vaughan, Wood, Young, and Zabel (P, S, T, V, W, Y, Z). The professors give their lectures in order, from first to seventh.

### Game Setup

This looks like a simple linear/sequencing game, but it’s a bit complex due to the fourth and sixth rules.

The first three rules are straightforward ordering rules, though they can’t be combined:

The fourth rule combines with the second rule. It says S can be 3rd at the latest.

So, S can only be 2nd or third since T goes before S. I prefer to make two scenarios, one with S in third and one with S in second.

This allows you to make separate deductions for each diagram, and it takes two rules out of your head and puts them directly on the diagram.

I drew the 5th rule directly on the diagram as well (Y is not last).

Instead of making two scenarios, you could draw ‘not S’ under spaces 4-7. Which option you go with is a personal choice, pick whichever feels more natural.

### Remember that S can’t go later third

This rule about S going third at latest is one that you should internalize though. It’s the rule most students forget, and the reason they don’t make deductions. I keep space in my head to memorize one crucial rule for every game, and things go faster and much smoother.

The final rule is complicated. If Y is before Z, then P is first:

Here’s the contrapositive:

(The V-Z rule fits well on the contrapositive, so I included it as a reminder.)

Note in the second scenario, P can’t be first, so this contrapositive applies.

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When the answer gets to the contrapositive of the final rule, Z appears as part of the contrapositive which confuses me. Where did Z’ come from?

It’s just a reminder. We know V comes before Z, so it seemed natural to me to add the V – Z element to that rule.

Whereas in the regular form, adding V to “Y – Z –> P1” would seem confusing.

It’s just a stylistic preference that reduces mental work. You can add it or leave it off as you prefer.

Why can’t S go third?

Oops. That was a typo in my heading. I should have said “can’t go later than third”. Thanks!

Isn’t the last rule a biconditional? Since it’s “if but only if”, so wouldn’t your arrow go both ways?

That’s correct! If you’d like, you can draw it as a double-ended arrow.