Decompositional reasoning
This is the breaking down of an issue into its constituent parts, analyzing these parts individually and using that analysis to draw a conclusion on the whole.
This approach is very useful in deconstructing your opponent’s arguments: break their arguments down into individual points and refute each of those points and you will have refuted it as a whole.
The obvious problem with decompositional reasoning is that most things are usually more than just a sum of their parts. It is useful all the same as a way of getting a glimpse into the inner workings of an issue, gauging a general feel of how it all fits together.
Systemic reasoning
This is the opposite of decompositional arguments in that it considers the whole of a system, overcoming the fact that a system is not only equal to the sum of its parts, by taking into account the relationships between the parts. The parts could be any number and variety of factors, from abstract theoretical considerations to real-world consequences, physical limitations and more. You can use decomposition to first identify the parts, then further take into account the relationships between them.
There are two types of systems to take into account: closed systems are those which are self-contained, meaning the parts only interact with each other, and open systems, where the parts are also subject to outside influence. The vast majority of systems you will encounter are going to be open – nothing exists in a vacuum, in the colloquial sense. Scientists will tell you that even a vacuum has radiation and all sorts of quantum entanglements popping in and out of it. We can take another cue from scientists, though, by assuming the system you are looking at is a closed system – it vastly simplifies the problem and allows you to draw conclusions about it without a lot of fuss.
Make a point of acknowledging this to your opponent, though, and once the base considerations you have to make have been accounted for you can then introduce the most pertinent outside elements. It’s almost impossible to take into account every single thing that affects your argument – you’d have to factor everything that happens in the entire universe to whether you should step out of the door in the morning in that case! Therefore, you and your opponent will have to find common ground on where you can stop.
