Quine's obfuscative confusion of what there isn't as what there is is only definitive in that it defines Quine as being in this instance - seriously mistaken.

Professor Quine's reificatively useful fiction is actually an ontologically committed claim which simply shifts the logico-ontological implication or existential significational burden of TO BE from (the possibility) of being in some unstated state as some unstated object, to that of actually BEING in an unstated existential modality as an unstated non-object.

Some Definitions of the term Variable

* something that is likely to vary; something that is subject to variation

* the weather is one variable to be considered

* a quantity that can assume any of a set of values

* liable to or capable of change

* variable star: a star that varies noticeably in brightness

* varying: marked by diversity or difference; "the varying angles of roof slope"; "nature is infinitely variable"

* a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity. [2]

The usefully fictive reificatives above lack material denotata. They bespeak of the manner in which the attributorial human catagorisors exist rather than the manner in which the the entiatic attributees exist.

The reifications: change, state, variation, variable, value, diversity, difference, possibility, something, quantities, capabilities, changeabilities, symbols, mathematical or logical expressions, etc. do not exist and are utterly useless symbols for serious ontological description.

The term to be cannot be said to refer to a modality of an existing object because:

(a) *Existence* does not exist - only the changing (existing) object exists.

(b) *To be* something does not exist either - only *becoming* something is an accurate ontological description of an object. For example every seven years the human body has been completely replaced by new cells. (compare The Ship of Theseus)

(c) The terms value and variable do not stand forth or cause to stand, etc. but are already modalities which are attributed to objects in order to qualify such concrete nouns and as such cannot have further modalic layers assigned to them as Quine attempts to do so. Such an bizarre ontological practice leads to infinite regression.

1384, from O. Fr. existence, from L. L. existentem "existent," prp. of L. existere "stand forth, appear," and, as a secondary meaning, "exist;" from ex- "forth" + sistere "cause to stand."

(d) All that Quine achieves is to characterise, to be as something that is not a descriptive modalic variability of an object, but something that acts as a descriptive variable of the modality of a logically useful but ontologically inexistent non-object.

(e) In addition Quine assumes the layman's error that to be is the uninflected form of the stem /be/ (used in the sense of /be/ as an unspecified state of being something or other (not mentioned) when in fact the /to/ adds an inflectionality which can bestow to be with intentionality, futurity, locativity and a host of other psychological, occupational, biological abstractive possibilities in its sentential employment, as in:

Bill is a father *to be*. Phyllis is going *to be* a mother. John is studying *to be* a doctor. Jane is said *to be* suffering from cancer. I think its going *to be* raining by nightfall. Eric is aid *to be* living in Tangier. etc.

(f) The ever-changing human exists in a modality of attributing classificatory descriptio of objects in the belief that in some occult fashion man's homocentric *values* are magically instantiated, transposed, infused and intrinsically absorbed by the categorised object. Objects exist in the way, manner and mode in which they exist  - it may be tautologous - but it is a fact. A dog, a mountain and a hat-pin exist in  the particular ever-changing molecular configuration in which they are present in the cosmos in a particular nano-second  of what humans imagine to be an interstice of time- utterly irrespective of what human linguistic signs are arbitrarily attributed to them in order that homosapiens  may mentally signify and representationally store such significata to target denotata which match the  collocations of chemico-electric data in their neural nets.

References:

[1] Quine. Willard Van Orman. "On What There Is," first published in the Review of Metaphysics. 1948. The article is included in Quine's book, From a Logical Point of View (Harper & Row, New York: 1953).