Principles: These are the fundamental, innate aspects of language that are universal across all human languages. They represent hardwired, inflexible rules that all languages must adhere to. Think of them as the underlying architecture of the human language faculty. Examples might include:
* Structure Dependency: Grammatical operations (like forming questions) depend on the hierarchical structure of a sentence, not just the linear order of words.
* X-bar Theory: A theory that posits a universal hierarchical structure for phrases in all languages.
* The Projection Principle: The syntactic representation of a sentence must reflect the lexical properties of the words involved.
These principles are not learned; they are part of our biological endowment. They constrain the possible forms a language can take.
Parameters: These are the aspects of grammar that *vary* across languages. They are like switches that can be set in different ways, resulting in the diversity of languages we observe. They are the points where languages can differ, while still operating within the constraints of the universal principles. Examples include:
* Head-directionality parameter: Whether the head of a phrase (e.g., the verb in a verb phrase) precedes or follows its complement (e.g., the object). English is head-initial (verb before object), while Japanese is head-final (verb after object).
* Null subject parameter: Whether a language allows sentences without overt subjects (like in many Romance languages).
* Pro-drop parameter: Similar to null subject, determining whether pronouns can be omitted.
Parameters are considered to be innate, but their *setting* is determined by experience – the child learns the specific setting of the parameters of their native language through exposure. The principles, however, remain invariant.
In short: Principles are the universal, unchangeable rules; parameters are the variable settings that account for cross-linguistic differences, all within the framework defined by the universal principles. The interaction of principles and parameters allows for a system that is both universal (all languages share a common foundation) and diverse (languages differ in specific ways).