Blocking vs. Conditional statements in Grouping LG

[psotlani]

Hi,

I've been practicing the grouping logic games at the end of Ch5, in the Logic games bible 2017, and I seem to have trouble differentiating when I can use a block vs a conditional statement.

In Game2, June 1997 the following statement: "L is seated at the same table as V" allowed for an LV block. However,
In Game3, Dec 2004, the statement "Wendy appears in every photo that Selma appears in" results in a conditional statement S W

I had originally made a conditional statement in game 2 - though it can be represented as a block. I'm wondering why that is? Does it have to do with how the rest of the question is formed???

Thanks in advance!

-Parnian

[Adam Tyson]

Thanks for asking, psotlani - let me see if I can help out here.

In the first game you referenced, each of our variables will appear only once. L and V will be in the same group, and not in any other group. That, and the fact that the rule has no conditional language, makes the block the simplest, clearest way to represent that rule. Attach those two at the hip and move them as a unit. A conditional rule of L V would suggest that L in a group forces V into that group, but that V could also be in group without L. That cannot happen here, so the conditional approach is less accurate (and more confusing) than the block approach.

The second game is very different. First, there are potentially dozens, hundreds, billions of photographs, so there isn't just one group in which to place the variables. While some of the photos may have both W and S, other photos may have W without S. They are not attached at the hip! A block would be inappropriate because it would visually suggest that W and S must always be together, which is an incorrect inference. Also, the conditional language ("every") points to this approach. The presence of the sufficient condition, S, guarantees the presence of the necessary condition, W, but the necessary condition could also appear all by itself (except not really, because other rules then lead us to the inference that W is sufficient for Y also being in a photo, but that's another story).

Basically, if the rule is conditional, diagram it conditionally. If it sets up a single, fixed, spatial relationship, use a block.

I hope that helps! Good luck in your continued studies!