Philosophy of Language
Regarding Natural Language：All human child are equipped to be able to learn any natural language. (Unlike any other animals) the human child are able to recognize noise/gestures, whatever it may be particularly, and match them with meanings,
Regarding Programming language: Programming language need to be settled before computers can match signals with what to process.
Takeaway: something is already there so that persons are capable of learning languages. This universally shared thing is compatible with the diversity of languages. Linguistic Convention plays a significant role in settle down which language system is actually acquired. Had there not be such a thing that enables children to learn, various languages would have not existed. (For ppl to learn new vocabularies via a dictionary, they have to already understand how this language works.)
Likewise, persons are equipped (might be the capability to recognize/grasps moral reasons) before they can adopt any (systematic) moral principle.
Had not be equipped, normality (should/ought) makes no sense at all? (A sense of justice, for example, is not some objects that ppl can directly appoint to. To “teach” ppl about the sense of justice, we might just hope the other person had similar ideas/experience already. Had persons not already got a grasp of the reference of ‘justice’, they cannot match it with the noise/signs of justice.
Four Analogy wishing to draw:
A Capability to learning a specific natural languages-Capability to acquire a specific system of moral principle
B. Diversity in Moral Principle -Diversity in Natural Language
C. Moral Convention -Linguistic Convention
D. Learning (new) words-Learning abstract moral concepts
A is universally shared
A is a necessary condition for BCD
A is compatible with B
C helps select which specific system to implant (possibly via social learning)
D based on A & C.
In short, if analogy I wish to draw is right, it would indirectly support moral realism and argue for the compatibility between moral realism and diverse moral principles.
Differs from Chomsky: Capability to acquire language VS Universal Grammar (Chomsky)