I'm reading "Meaning and the English Verb" by Geoffrey Leech and in the paragraph §113 on page 71 he states the following:
First, the ways of referring to the future dealt with in this chapter illustrate the point made in §5: that the Present Tense, from the semantic point of view as well as syntactically, would be best described as 'non-past'. We have seen that all these future-referring constructions are variations on the Present Tense, with the very minor exception of the future subordinate use of the Past (see §102c) - even including the 'non-past' modal auxiliaries will / shall, to which we turn again in the next chapter. In other words, the Present Tense, in a broad sense, encompasses both present and future domains of time.
However, in English the major formal distinction of Present and Past tenses can be associated with two major TIME ZONES, 'past' and 'non-past', so that future time is subsumed under 'non-past'. This helps to explain why English, which does not have a Future tense as such, uses Present tense to express future time.
I know what he means by "from the semantic point of view", but I do not understand what he means by "syntactically" in this context.
So what does it mean when he says that "The Present tense would be syntactically best described as 'non-past'"?