I'm tempted take advantage of this chaos among the "experts" and crown myself a de facto expert on the subject. But maybe I might serve the "debate" a bit well by deferring to that other Oracle of internet truth. Here is what the venerable Wikipedia (my boldface for emphasis) has to say...
There is no universally accepted criterion for distinguishing a language from a dialect. A framework that may aid in analyzing the issues is provided by the linguistics concepts of Ausbausprache, Abstandsprache and Dachsprache. A number of rough measures exist, sometimes leading to contradictory results. Some linguists do not differentiate between languages and dialects, i.e. languages are dialects and vice versa. The distinction is therefore subjective and depends on the user's frame of reference. Note also that the terms are not by themselves mutually exclusive; there is by itself nothing contradictory in the statement that "the language of the Pennsylvania Dutch is a dialect of German". However, the term dialect always implies a relation between languages: if language X is called a dialect, this implies that the speaker considers X a dialect of some other language Y, which then usually is some standard language.
Language varieties are often called dialects rather than languages:
- because they have no standard or codified form,
- because the speakers of the given language do not have a state of their own,
- because they are rarely or never used in writing (outside reported speech)
- or because they lack prestige with respect to some other, often standardised, variety.
But just going by the latter four-point criteria, it seems Tagalog fails in three out of the four success factors for it to be considered a bona fide "language". Indeed, the last one begs an interesting question:
Do we see Tagalog as a prestigious form of communication?