Here’s the thing. There is descriptive research and there is experimental research. Descriptive research on its own can be informative and tell you something about a system, but at some point, you’ve got to get in there, change something, and see what happens. Just reporting on what you see under the microscope or on a blot is interesting, but it won’t explain why you are seeing what you are seeing. Experimental research tests a hypothesis, which means altering a variable in the known system and seeing what happens – the result will lead you to reject or fail to reject your hypothesis. Of course you’ll repeat the experiment in exactly the same way several times so you can be confident in your results. But then you’ll need to try changing something else, repeat, repeat, repeat, and so on.
In a research grant proposal (and I’m coming from the NIH perspective here), each aim should independently test your central hypothesis from different angles. You might use different methods or combinations of methods, or work at different levels (biochemical, molecular, cellular, tissue, organism, ecosystem, etc). What you learn in each aim will come together to shed light on the system you are studying.
Now, one of those aims might be descriptive, but I would argue that a purely descriptive aim is going to be your weakest aim. Devoting an entire aim to descriptive science breaks two rules in scientific grantwriting – descriptive science is not able to test your central hypothesis, and your aims must not depend on each other. (Because if one aim fails, there goes the entire proposal.) Any aim that is purely descriptive will be dependent on what you find in the other two aims.
The same descriptive vs. experimental idea applies to journal articles too. If your article is descriptive, you’ve got half a story. Sorry, but it’s true. The best, most compelling, field-advancing, paradigm-shifting articles are those that have a clear hypothesis, describe what is known, and then describe a logical progression of changes made to the known and what happened. I know you’ve heard this before, but the best paper tells a story, starts by describing the known system and posing a hypothesis, and then leading the reader through each experiment, discovery, experiment, discovery, until the Discussion section brings the reader back around and gives some context. I know, some journals will accept purely descriptive articles, but not the top-tier journals.
It’s getting more and more competitive out there – for research grant funding and publishing articles. So get in there. Get your hands dirty. Know your system, pose a hypothesis about the system, then change something and see what happens. Then change something else and see what happens. And if you need help telling the resulting story and getting other people to understand exactly what it is you’re doing, I’ve got your back.