Meaningful

A sentence is meaningful, in which it can be proved or dis-proved.

Since, "A sentence is meaningful" cannot be proved or dis-proved, therefore, it is meaningless. however, the above sentence is a definition. it is useful, according to how we use it. thus, "meaningful" is not quite a daily used word "meaningful".

most of our sentences are not meaningful, like those express our feeling, imagination. "oh, the moon is beautiful!" "Mary is pretty" are this kind. "my father is 47 years-old." "the sun's surface is about 6000 degree" are meaningful sentences. as we can see, meaningful sentence is those can give us a way to know about the world, and non-meaningful sentence can give us an imagination to other feeling.

"Alexander the Great was born at June 10, 323BC", is it a meaningful sentence? or, can we prove or disprove it? this is not so obvious to do so. and thanks for historians, we believe it is truth, and it is not just a claim or imagination.

"ghost exist everywhere", so far for human intelligence, it is not clear yet. so, this sentence give no information about the physical world but human imagination. another obvious example is "God create the world", and "human have free-will".

when we counter this kind of sentences, changed the view point may be help. for example, give more concrete definition. "what is god?" "what is free-will?" as long as we can define those concept clearly, may be we can make a more proper sentence.