Some species of tarantula make good pets. However, no creature with poison fangs makes a good pet. Therefore, not all...

Carys on December 23 at 12:11AM

Parallel reasoning question

how does answer A parallel the stimulus. What is the reasoning behind it?

1 Reply

Ravi on December 23 at 08:19AM

@carysdavies,

Great question. In mapping the stimulus, we have

tarantula - -some - -good pet - ->/poison fangs

The stimulus then concludes that not all tarantula species have poison fangs

tarantula - -some - -/poison fangs

in translating the conclusion, make sure you negate the conditional statement properly.

The conclusion reads not (tarantula - ->poison fangs)

This is a negation of this conditional statement, which means there is at least one tarantula that doesn't have poison fangs

tarantula and /poison fangs

This means the same thing as tarantula - -some - -/poison fangs

The basic structure of the stimulus is A some B, B - ->C, therefore A some C

This is a valid argument form.

Answer choice A states that none of the poetry written by Strawn has a regular meter.

poetry Strawn - ->/regular meter

It also states that some of the poems in this collection have a regular meter

poems in this collection - -some - -regular meter

In order to link the two premises together, we need to take the contrapositive of the first premise

regular meter - ->/poetry Strawn

We can now link this up with the second premise, so we have

poems in this collection - -some - -regular meter - ->/poetry Strawn

So far, we have A some B, B - ->C. What do we need for it to match the stimulus? We need A some C

So, if it says poems in this collection - -some - -/poetry Strawn, then we have our answer

The conclusion of A says at least some poems in this collection were not written by Strawn.

A - -some - -/poetry Strawn

This is exactly what we needed (we needed A some C), so this is our answer.

The key for this problem is to take the contrapositive of the first premise in answer A so that you can clearly see the link that the two premises make between A (poems in this collection) and C (poetry not written by Strawn)

Does this help? Let us know if you have more questions!