When considering an argument or a position, it’s important to be able to find out what is being assumed without being stated because often arguers, sometimes unawares, fail to state problematic premises.

Finding out hidden assumptions requires having a clear understanding of the workings of the argument in question. For example, consider the following argument:

“Being miserable requires the capacity to remember past pains and foresee future ones. However, this capacity presupposes having a sense of the self. Consequently, animals cannot be miserable, and therefore they cannot suffer. But we can suffer. Hence the needs of animals should be subordinated to ours.”

The argument assumes, without stating it, the following EXCEPT:

1. Animals don’t have a sense of the self and/or lack the capacity to remember past pains and foresee future ones

2. Only beings that can feel miserable can suffer

3. The needs of beings that can suffer take precedence over those of being that cannot suffer

4. Animals cannot feel pain

5. Only humans can suffer

Before proceeding, one must understand the logical working of the argument. It’s constituted by conditional statements, and therefore likely to us MP, MT, or the hypothetical syllogism.

For the answers, see below.

The correct answers are (4) and (5). Here’s why. (1) is needed for the subconclusion that animals cannot be miserable, and (2) for the further subconclusion that animals cannot suffer. (3) is needed to go from the claim that animals cannot suffer to the argument’s conclusion that their needs should be subordinated to ours. (4) is not needed at all, as the argument rests not on whether animals can feel pain or not but on whether they can remember having felt pain and foresee future pains they may have to endure. So, although if they cannot feel pain then they cannot remember feeling pain, the converse is not true: an animal could feel pain without remembering feeling it afterwards; (5) is not required unless one makes the previous assumption that all sentient beings are either human or animal, and the argument neither makes nor needs to make such an assumption. For example, the strength of the argument would not be diminished if, say, angels exist and can suffer.

As you can see from the example, when you have identified a possible presupposition P, ask yourself whether the negation of P damages the argument; if it does, then P is a presupposition; if it does not, then it isn’t.

Consider now the following argument:

“As humans have a common nature, a set of basic common characteristics, they share some basic needs and interests. Some moral systems do better than others at satisfying such needs and interests; hence, there is one objectively valid universal single morality applicable to the whole humanity, namely the one that satisfies those needs and interest best.”

The argument assumes, without stating it, that:

1. All human beings are the same in most respects

2. There is a system of morality applicable to all human beings

3. If moral systems differ in their capacity to satisfy basic human needs and interests, then there is a single one that satisfies such needs and interests best.

4. Human beings share most needs and interests

5. Morality must satisfy basic human needs and interests

For the answers, see below.

The correct answers are (3) and (5). (1) can be false while it remains true that humans have a common nature, as there is no reason why human nature should be constituted by most properties humans have For example, a few basic properties may be biologically given, and make up our nature, and most culturally given. (2) is the conclusion of the argument and is not presupposed by any of the premises. Taking the conclusion as a presupposition is a common mistake one must carefully avoid. (3) is the needed link between the claim that there are different systems of morality satisfying basic human needs with different levels of success and the claim that there is one system that satisfies those needs best. Without that there would be no assurance that there is one universal system of morality. (4) need not be true because what’s needed is that humans share some basic needs and interests that constitute human nature, not that they share most needs and interests. (5) is needed because it links morality to the satisfaction of basic human needs and interests; without this assumption, there would be no way to move from the claim about common needs and interests to that about a universal morality.