It's both, and that's the problem.
Some marketers are scientists. They test and measure. They do the math. They understand the impact of that spend in that market at that time with that message. They can understand the analytics and find the truth.
This sort of marketing works when it works, but it usually doesn't. That's because we're dealing with humans, the wild card in the system.
The other marketers are artists. They inspire and challenge and connect. These marketers are starting from scratch, creating movements, telling jokes and surprising people. Scientists aren't good at that.
The problem is caused by two things:
1. Outsiders are confused. Which are we? When we're artists sometimes and scientists other times, we often seem like charlatans, because we're associating scientific results with artistic endeavors.
2. We're confused. If you don't know if you're doing a science project or an art project, you'll probably emphasize the wrong elements. If you go to school to study marketing and the blowhard professor acts like she's teaching you science, you'll waste a lot of time trying to apply taxonomy and hypotheses to something that is essentially a gut decision. And vice versa.
We need hats. The hat of the scientist and the hat of the artist. You can only wear one hat at a time, which is why I didn't suggest that we need gloves.
Figure out what sort of marketing you're going to do today and go do that.