Brevity is no insurance against ambiguity, because terseness doesn't always allow clarification. One insurance against ambiguity is to establish mutually agreed upon working definitions of terms used, preferably aligned to their standard usage. Javed Akhtar
emphasizes the need for working definitions often, and this can help avoid weaseling and equivocation with words like '
spirituality'. This investment in working definition
can save much trouble, is illustrated deftly in
this article which is also linked often here. Hence the attempt in
post #6 to disambiguate the meanings of often willfully misunderstood terms.
Having said that, let us come to the question raised above i.e.
Can Science function without Realism? What are the foundations of Science that are 'at par' with Realism?
The only thing Science can't function without is the Scientific Method. Other 'isms' are associated with it largely in attempts to
supply meta-narratives of Science as a human endeavour. There is no single definitive meta-narrative of
what constitutes the human endeavour that is Science, any more than there is one for Sport or Religion. However, any activity maybe recognized as belonging to one or the other endeavour by observing some commonly occurring traits eg. activities analogous to worship and veneration belong to Religion and activities involving experiments to test claims belong to Science. Here is a list of some traits of scientific endeavours, which led to it being conveniently and aptly associated with certain 'isms', though none is synonymous with Science itself:
(i)
Realism: In theory, it is possible for a scientist who believes that all objects in the world and in the lab are ideas in the 'Mind of God', to follow the Scientific Method to the letter by going through the motions, and report experimental results like "A heavier object (as imagined by the Mind of God) doesn't fall faster than a lighter object (as imagined by the Mind of God)." One thing to note is that even for someone attempting to understand the Mind of God, understanding is not furthered or promoted by repeatedly adding in the parts in parentheses above! It helps just as well to say "A heavier object doesn't fall faster than a lighter object." and function as if the objects were public and neutral. As the scientific enterprise concerns itself with the behavior of objects (eg. how they fall) rather than ontological claims about what they are(eg. 'public and neutral' or thoughts in the Mind of God), a scientist in the lab, irrespective of her ontological stance, functions
as though Realism is what is being subscribed.
(ii)
Falsificationism: Testable hypotheses are indispensable to the scientific method and the
problem of induction precludes verificationism, thereby leading to falsificationism being treated as the philosophical underpinning of all scientific enterprise. However this paradigm, which only places the requirement of practicability of an experiment to test a claim,
doesn't fully circumscribe scientific enterprise, especially those parts about how claims are arrived at in the first place. Many gedankenexperiments are in fact quite literally impracticable to perform, but the scientific claims they yield can later be operated upon in a falsificationist paradigm. This 'ism' too therefore is related and compatible with the scientific method though not synonymous.
(iii)
Naturalism: A practitioner of the scientific method will run into fewer contradictions while functioning within a naturalist rather than mystical worldview because:
(1) Just like repeatedly saying 'object(as imagined in the Mind of God)' does not promote improving scientific description more than simply saying 'object',
positing supernatural entities does not add explanatory power to our descriptions of natural phenomena.
(2) Treating the Principle of Uniformity in Nature i.e. 'Laws are discernible in Nature and they can be used to make predictions.' as a working assumption (related to the notion of background independence) likewise isn't subject to any more limitations than treating natural phenomena as inscrutable vagaries of a Supernatural Being.
The question of which of these 'isms' are 'on par with each other' in their importance to Science, first needs a working notion of what parity is here in the first place. From the perspective of an 'equal opportunity offender', there is parity among all organized religions in that all of them present challenges to living a life in accord to Reason to Compassion, even though there maybe mind-boggling diversity in their rituals and practices. Likewise one 'parity' which the 'isms' above share vis-a-vis the Scientific Method is a readier compatibility with the Scientific Method than their rival 'isms'.