What is the most fundamental activity of science?
The most fundamental activity of science is to try to discover the truth. Scientists are concerned with studying how different parts of the universe behave. This can encompass everything from grand theories in theoretical physics as to the fundamental nature of the entire universe and what keeps it all together to something as specific as how a particular species of frog mates. But the fundamental goal of the activities in both disciplines is the same, to seek the truth of the subject. Since much of science deals with things that cannot be directly observed with the basic human senses, we must have a scientific method as a means to the systemic discovery of the truth, or at least as close to the truth as scientific observation can allow.