Is science a tool or a subject?
Thanks for the request, and apologies for being quite slow to respond.
Unlike the other responses that I've included in other questions that you've directed, I'll give a flat out "neither" to this question.
I don't see science as something akin to a filtration system that produces knowledge from a collection of sense data. As mentioned by various philosophers of science in the past decade, especially by Feyerabend, the scientific method that is highly prized by public understanding of the enterprise is never a closed system. In most time, the scientific method is whatever that governs the standard work procedures of the scientists, and they have inherent interests that are outside the scientific endeavour.
Because I'm not very concerned about biology and chemistry, I will narrow the discussion to physics, because I believe it is currently facing a problem called the "debt of empirical proof". Scientific discoveries are usually initiated by theoretical extensions of our current theories, and then later verified by empirical discoveries. The most relevant example that comes to my mind is Dirac's equation, which he derived from Einstein's, to account for spinors. The Dirac equation involves a mathematically necessary expansion of the wave-function matrices from two to four elements, and he and contemporaries had no idea why. It was only much later in the 1950s that there were empirical discoveries of anti-matter, and the expansion was necessary to account for the spin of anti-particle.
If theoretical advancements only emerge in such a way, then science could hardly be described as an instrument. If science is taken to be an instrument to produce knowledge of the empirical world, it must have some predictability when we plug sensuous data to the scientific method, to yield scientific knowledge. As mentioned, the scientific method isn't really that rigorous, strictly empirical scientific method that most people take to be, and in modern times the theory holds up itself before the empirical certainty is provided. In that respect, we can't always expect science to churn out knowledge of the empirical world. Some times, most of what we know from science faces upheavals and new theoretical templates are needed.
Like philosophy, I am quite against characterisations of fields of knowledge into distinct subjects. All fields of knowledge are inevitably linked together in some way, and our perception of them as individual regions of studies result from deliberate limitation of the questions that we deal with. Education systems employ subjects as tools to inculcate knowledge that are exam-oriented, hence it is no wonder why many people often pick their university courses based on its practical utility (e.g. how much does studying philosophy earn you in the future? What jobs do you get to choose?).
Instrumental connotations aside, science as a subject is seen as closed off within itself, having textbook-based standards of correctness that does not reflect science as a field of knowledge. While there is an educational need to cultivate competency and certain traits through science, this aspect should fall off once the foundations are being laid upon the students' mind. Carrying on that weight into the frontiers of scientific discovery will only bog down creative tendencies necessary for the field.
Education systems in many countries have been quite driven to inspire students to develop interest in science by exposing to various forms of information beyond curriculum. However, I don't think diversifying types of information will be useful, since the students are taught to place them into the respective pigeonholes that are educated with in school. To "inspire curiosity", the more appropriate solution is to expose them to how scientific knowledge is being constructed, and engage them in thinking about issues that science deals with on the whole.
I don't think we should see science that something that we can employ to solve problems as well. As from the previous portion, most of the time, science generates more problems than resolving them, and usually resolving problems generate more problems that are even more fundamental. Moreover, using science to solve problems simply constricts the creative necessity of the field of knowledge - relativity certainly didn't come from the results of Newtonian mechanics, but came from a re-thinking of assumptions (viz. the world as a fixed, Cartesian map of coordinates with a universal frame of reference) inherent in the paradigm.
I've mentioned previously in an answer that I see science not as progressing towards some ultimate truth, but as itself an expanding bubble, which truth refers back to itself. Truth in science is only recognisable as truth, when it is considered as a truth of science.
Characterisation of science with something external to it will only distort it as a field containing truth. Be it an independent field of knowledge, or as instrumental to some external notion of truth, or as a problem-solving mechanism, science will never be grasped in its entirety, and will be effectively limited in its scope and potential. Science is a truth in and for itself, and never for something else.
Science is "The Scientific Method" - a means to reason about the universe and get an idea of what's true and what's not.
Science is also a collection of experimental results, observations and conclusions that were obtained from them.
The first is a "tool", the second is a "subject".
The idea of the scientific method as a tool is an interesting one. For example - if you play a computer game like (say) Minecraft that allows you to play around in its' virtual environment - then you can use the scientific method to propose ideas about how the Minecraft "universe" works - you can come up with hypotheses, do experiments, come to conclusions.
In that situation, the laws of physics from "The Real World" don't apply...the law of conservation of mass, for example, does not work in the Minecraft universe...and we can do experiments to demonstrate that.
So here we're using the Scientific Method as a tool, quite separately from the pile of "real world" experimental data, observations and conclusions.
Conversely, many people in engineering and other technology-based positions use the result from science to do great things - but without using The Scientific Method.
So clearly the two parts of science are somewhat independent. You can definitely have one without the other.
I think it's more of a tool.
Articulating reality in specific ways allows practical utility.
For example, Newton's paradigm is supposedly ‘wrong' about time being linear everywhere, yet it still has usage in engineering (constructing planes and buildings) today. Similarly, Einstein's theory posits that time passes by more quickly in space, which allowed the invention of the GPS.
We can't say that either is right or wrong. They just have different applications.
Because there are so many ways of articulating reality, the different paradigms, which are seemingly incompatible (different definitions of time and even gravity), I do think that we're only creating different models to represent reality, which can be used in different ways. This makes science a subject as it employs different conceptual apparatuses (models).
I'd say it's both.
According to Merriam-Webster, one of the Definition of SCIENCE is "something (such as a sport or technique) that may be studied or learned like systematized knowledge", which is where the subject comes in. This article by Degrasse-Tyson on the Huffington Post, What Science Is -- and How and Why It Works, may be useful.
It's a subject we study in school, in pursuit of something that fits in with Merriam-Webster's definition.
It's a tool we use to understand what we don't know.
This quote by Arthur C. Clarke sums it up best: "Magic's just science that we don't understand yet."
Science is both a tool and a subject. In fact, all subjects of study can also be tools. I am currently using language as a tool to communicate with you but I could also study the English language. Even art can be a tool for advertising but it is also a subject for study.
Science is no different. We can study it but we can also use it as a tool to accomplish something.