Editorialist: Some people argue that we have an obligation not to cut down trees. However, there can be no obligatio...

Kath on September 28, 2019

Necessary assumptoin

I son understand why A is not the correct answer. There is a change in the stimulus from right to obligation. Could you explain the whole stimulus and each answer choices?

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Irina on September 29, 2019


This is a challenging question. Let's look at the structure of the argument:

We have the following premises:
(1) Have an obligation to cut trees.
(2) No obligation to an entity unless the entity corresponding right.
We can diagram this statement as follows:

Obligation -> right
~right -> ~no obligation

(3) So if we have an obligation toward trees, then trees have rights.
This is a proper inference from the premise above:
Obligation -> right

But notice that the argument switches from obligation/ right to an entity to obligation toward trees specifically, so the inference is only valid if we assume that the obligation is owed to trees and an entity = trees for the purposes of this argument.

(4) Trees do not have rights

~ rights

(5) Therefore, we have no obligation to trees.

~ obligation

This is another proper inference from premise (3) as long as trees are the entity that an obligation is owed to.

Let's look at the answer choices:

(A) If an entity has a right to a certain treatment, we have an obligation to treat it that way.
Incorrect. This is a mistaken reversal of premise (2), which says obligation -> right, whereas (A) says right -> obligation .

(B) Any entity that has rights also has obligations.
Incorrect. The argument is not saying that an entity has to have both rights and obligations, only that if someone else owes an entity an obligation, an entity must have a corresponding right.

(C) Only conscious entities are the sort of things that can have rights.
Incorrect. This is not a required assumption because the argument only refers specifically to trees, so it is possible for other unconscious entities other than trees to have rights and for the argument to still make sense.

(D) Avoiding cutting down trees is not an obligation owed to some entity other than trees.
Correct. If we negate this answer choice and say that it is an obligation owed to some other entity, the argument falls apart because then it is this other entity that must have a corresponding right rather than trees.

(E) One does not always have a right not to cut down trees on one's own property.
Incorrect. This answer choice is out of scope of the argument. The argument is about an obligation NOT to cut down trees, not a right to cut down trees, and the argument is general rather than about rights on one's property.

Let me know if this makes sense and if you need any further clarification.

Kath on September 29, 2019

Thank you so much! Please help me check if I am right from your answer. So, from answer choice D, if the obligation not cutting down trees is an obligation owed to some other entity (like a cat), according to the principle "obligation to an entity - >the entity has the corresponding right", the entity (cat) must have the right not to be cut down. However, the cat can not have such right. Therefore, the argument in the stimulus falls apart. Is it correct?

Kath on September 29, 2019

Another reason I am confused is that the argument in the stimulus is complete. I used to think necessary assumption question only appears when the argument has a gap.

Irina on September 30, 2019


That's correct, if the obligation is owed to some other entity (like a cat), then the argument no longer makes sense. And there is a gap in the argument between premise (2) and (3):
(2) No obligation to an entity unless the entity has a corresponding right
Obligation to an entity -> entity has right


(3) So if we have an obligation toward trees, then trees have rights.
Obligation to trees - > trees have rights

The gap needs to say that entity = trees for the argument to follow logically.