The word "science" has changed its meaning as we pass from antiquity and the Middle Ages to modern times, especially to the nineteenth and twentieth centuries.
Today it means the observational or investigative sciences sometimes called the empirical and experimental sciences. It must be added that the word "science" is also used to refer to mathematics, which is clearly nonempirical and nonivestigative.
The adjective "scientific" is used as a term of praise conferred on other disciplines: such disciplines employ methods which have a certain objectivity in their appeal to evidence which sets them apart from mere, unfounded opinion. Though history is not a science, nor is philosophy, nevertheless as branches of humanistic scholarship, both can be conducted in a manner that is praised when they are called scientific.
The word "science" derives from the Latin word scientia, for which the Greek equivalent is either episteme or doxa. In antiquity and the Middle Ages, the various branches of philosophy were called sciences. Today, from the point of view of the empirical sciences, when philosophers employ a praiseworthy method they are called scientific (See Knowledge.)
With the rise of positivism in the nineteenth and twentieth centuries, which asserts that empirically reliable knowledge is to be found only in the empirical and experimental sciences, it has become necessary to set investigative science apart for history, from mathematics, and from philosophy.
I have explained elsewhere in what manner the branches of philosophy, especially metaphysics (or philosophical theology) and philosophical psychology, can be properly compared with the empirical and experimental sciences with regard to agreement and disagreement, progress, and the criteria of truth and falsity.
It is of great interest that all the disciplines being compared (the empirical sciences, mathematics, history, and philosophy) have a history and a philosophy but no science (in the modern, positivistic sense) that is applicable to the understanding of the sciences themselves. There is no science of science.
Earlier. I wrote a methodological account of philosophy's past, present, and future. There I explained why philosophy has been so late in maturing. Philosophy has a brighter future in the centuries ahead.
If philosophy did not exist, we would have no moral philosophy as a branch of knowledge and we would have no understanding of science itself, for when scientists write about science, they do so as philosophers, not as scientists.