Indirect Grounding Through Nested Syllogisms PDF

§4.3 Indirect Grounding through Nested Syllogisms Advocacy would be much simpler if all premises were directly grounded —if the judge could look at the advocate's premises and understand them to be true at a glance. Unfortunately, it is often the case that advocates...

§4.3 Indirect Grounding through Nested Syllogisms Advocacy would be much simpler if all premises were directly grounded —if the judge could look at the advocate's premises and understand them to be true at a glance. Unfortunately, it is often the case that advocates must construct syllogistic arguments using premises that are not self-evidently true, and which require further explanation to gain acceptance. All premises must be grounded. But if a premise is not directly grounded how can its truth be demonstrated? Such premises must be grounded indirectly. Indirect grounding involves taking an ungrounded premise and linking it indirectly, through other syllogisms, to a directly grounded premise. Indirect grounding is a four-step process: 1. Identify the ungrounded premise. 2. Convert the ungrounded premise to the conclusion of a new syllogism. 3. Construct new premises for the new syllogism leading to the required conclusion. 4. Evaluate the new premises to see if they are directly grounded. If they are directly grounded, stop. If not, repeat the process until all premises are directly grounded. This procedure of indirect grounding results in a set of “nested” syllogisms that link the ultimate syllogism indirectly to a set of premises that are directly grounded and thus require no further justification. Here is an example of indirect grounding. Suppose you wish to persuade your local town council to install a traffic light at a dangerous intersection near your house, and you present the following argument: 1. Traffic lights should be installed at dangerous intersections. 2. The intersection of North Street and Main Street is dangerous. 3. Therefore, a traffic light should be installed at the intersection of North and Main. Now suppose that you judge the major premise to be adequately grounded as far as the town council is concerned; you think the council members will accept the major premise as self-evidently true. The minor premise, however, may present problems. Let's assume that it is not directly grounded. To ground the minor premise indirectly according to the method set out above, you must first convert the premise into the conclusion of a new syllogism: 1. 2. 3. Therefore, the intersection of North Street and Main Street is dangerous. The next step is to fill in the premises of this new syllogism. Note that performing this step forces you to analyze your own implicit assumptions and premises. Why do you think that this intersection is a dangerous one? Let's assume that you think the intersection is dangerous because there have been many accidents there—say, one a month. That information might give us the following syllogism: 1. An intersection is dangerous if it is the site of one or more accidents per month. 2. The intersection of North and Main is the site of at least one accident per month. 3. Therefore, the intersection of North and Main is dangerous. The final step is to see if the premises of the new syllogism are directly grounded. Are they? As we have seen, the answer to this question depends on the context. Perhaps most town councils would accept the major premise of this syllogism without further argument. If you think your council would, you may consider the major premise directly grounded. On the other hand, it is possible to imagine a town council requiring further explanation for the major premise. For example, the council might respond: “Dangerous compared to what? Maybe an accident rate of one per month makes the intersection a relatively safe one compared to other intersections in the town.” If you really wanted to be sure of making your case persuasively, you might decide to further ground the major premise of the new syllogism. You would again need to examine your own assumptions and premises: why do you think that an accident rate of one per month makes an intersection dangerous? Perhaps you might come up with a new syllogism along the following lines: 1. An intersection is dangerous if its monthly accident rate exceeds the average monthly accident rate for all intersections in the town. 2. The average monthly accident rate for all intersections in the town is just under one accident per month. 3. Therefore, an intersection is dangerous if it is the site of one or more accidents per month. As before, you would then need to ask yourself whether each of these premises is adequately grounded, and so on. Eventually, though, you will come to a point beyond which further explanation is impossible or unnecessary. When such a point is reached, your original syllogism is indirectly grounded. The following diagram summarizes the indirect grounding process set out above.