When we say

(1) It is raining in Waitarere

we are speaking in ordinary English. But our concern in this book is not with how to speak English per se. Still less is it how to teach the meaning of English sentences to anyone who does not understand English. We are simply using English as an example of a language in which sentences are being used which can illustrate the world–time parallel, and we choose English simply because readers of this book will already understand it. We are though concerned with how to analyse the truth or falsity of ordinary English sentences like (1). And we say that (1) is true at a time t iff there is rain in Waitarere at t. In other words

(2) ‘It is raining in Waitarere’ is true at a time t iff it is raining in Waitarere at t, i.e.,

(3) (1) is true at a time t iff it is raining in Waitarere at t.

Since what we want is an analysis of (1) we are treating (1) as a sentence of our object language. (3) is part of our metalanguage. One can present a grammar of Italian in English. Italian is the object language and English is the metalanguage. One can also present a grammar of English in English. The metalanguage in (3) is a version of English which makes reference to truth at a time.