I hold that you get the best understanding of something by looking at it from many different angles. You can think of this as cross-referencing. And the image I like to use as to how that cross-referencing works is the way a searchlight (or, rather, a set of searchlights) can probe and illuminate an object.
Generally I take this metaphor to apply to understanding anything whatsoever, but in order not to get bogged down in philosophical terms like ‘proposition’, ‘essence’ and wotnot, let’s look at how we might understand a ‘topic’ or a ‘subject’ such as you might meet at university.
Here’s a post I put on The Student Room (TSR) – a UK-based student forum – today (edited and tidied up to make it better to read). The response is to a student who is concerned about what to specialise in at university and whether there is anything on the curriculum that really matches their interest.
“The metaphor I like to use is of a searchlight. Imagine that what you are really interested in is out there – it could be development studies or the study of cities, human-computer interaction or global trade, anthropological studies of literature or neuroscience of music – whatever; but whatever you are interested in, it doesn’t fit neatly into one university department.
So you start by shining one searchlight towards the area you are interested in – let’s say you shine a light from the Geography department in the case where you are interested in development studies – but that only gives you one angle, so you get a bit of a lopsided view of development studies. So you shine a light from economics on development too. Now things are getting better. But they get a lot clearer still if you shine one or two more lights from other completely different sides, say from History or Statistics. If you then finally shine a light from, say, Anthropology, you are coming close to having a 360 degree illumination of the subject which is completely valid (indeed, it is arguably deeper than any single perspective), yet it is your own. But to arrive at this understanding you did not study a ‘subject’ in the undergraduate prospectus (development is not a subject on most undergraduate prospectuses).”
The point is simple, really: that to get the most rounded and balanced perspective of something, to get the best all-round understanding of something, it is usually best to view it from many different perspectives.
With regard to a subject you wish to study at university, this can often mean taking courses on the same ‘thing’ (or at least closely related things) in different departments.
Sure, the examples come easiest when thinking of things towards the social sciences/humanities end of the spectrum. But this is not always the case.
Even in physics, biology and chemistry there are certainly students (I was one) who benefit greatly from having a wider perspective than the one you can gain from just doing the problems in the textbooks or those set by the tutor. To really get at relativity and quantum mechanics, I would even go so far as to say that you have to go back to Mach, Einstein, Schrodinger and others to see the philosophical context in which they worked. Once you understand their problems and dilemmas, the things they were struggling to understand and the problems they were trying to solve, you get a better grasp of their solutions – and the new dilemmas that arose after them and persist to this day!
And even if you do not have a taste for historical or philosophical perspectives, there is no doubt that you would deepen your understanding and make it more flexible by taking, say, some courses on quantum mechanics from the Physics department and some from the Chemistry department.This, in its way, is also part of interdisciplinarity – another example of the value of interdisciplinary learning and an interdisciplinary approach to university undergraduate studies.
It is the ability to think round a concept or a subject, the ability to play with it and describe and use it in different ways, that demonstrates you really have a grasp of it. And that ability comes from viewing the concept, the thing you are studying, from many perspectives, from having it illuminated by searchlights from many sides.