Right, I am trying to explicate Millican's account of Strawson, not Strawson, and I am in no position now to check Strawson. However Millican and Wolfram are defenders
of Strawson, the latter studied with him, both seem quite good philosophers. So my own view is that, while it's possible they have seriously misunderstood Strawson,
they may well have got him right. If I were interested in Millican and Wolfram and Strawson, therefore, I would proceed on the working assumption that they may well
be understanding Strawson well enough and go on to at least understand how they defend him against the problem they think Quine poses. After all,
views like these are held, so, even if Strawson didn't hold it, it's worth seeing how Quine's objection to them can be rebutted--if it can. The Wolfran/Millican
objection to Quine is worth considering for its own sake.

If you haven't read it already, you might read Frege's Sense and Reference, which is the seminal work on this sort of issue and which
all of these discussions presuppose--not that everyone agrees with him. 

I probably haven't done a good job of explicating Millican on Wolfram on Strawson, so I will let Millican do his own work. Here is his own account of the alleged difficulty
for Strawson.

'On the Strawson/Wolfram account, two sentence utterances (or inscriptions etc.) make the same statement if they ‘say the same of the same object(s)’ (PLI p.36).  No doubt many subtle ambiguities and problems lurk beneath the surface of this apparently straightforward definition, but at least in many simple cases it seems fairly easy to apply.  Thus for example the two sentences:

            (1)        The Earth is inhabited

and      (2)        This planet is inhabited

will express one and the same statement, despite their verbal differences, provided only that the two are uttered simultaneously and that the latter is uttered by someone who is either on the Earth, or who is otherwise identifying the Earth as the planet to which reference is intended.  As long as both sentences are used to talk about the same object, namely the Earth, and as long as both are used to say the same about that object, namely that it is inhabited at the same particular time, then both express the same Strawsonian statement.

Central to this account is the notion of a referring expression, since it is definitive of a genuine referring expression that it serves only to pick out an object, and does not contribute in any other way to the statement expressed by a sentence in which it occurs.[1]  It is precisely for this reason that two referring expressions which designate the same object may be freely substituted for each other without altering the statement expressed.  Thus a theory of statements will not be complete until a ruling is made as to which kinds of expression may perform the function of genuine reference: names and demonstratives are obviously plausible candidates, but doubts may arise in the case of definite descriptions.  A Russellian analysis, for example, would view definite descriptions as disguised quantifiers, and would therefore refuse to count them as genuine referring expressions.  Strawson and Wolfram, on the other hand, reject the Russellian theory of descriptions, and both are happy to accept that a definite description can be used for the function of ‘uniquely referring’, though it does not follow that this is their only possible use (Strawson 1971 p.1;  QSNT pp.235-6; PLI pp.55-60).  In considering the Strawson/Wolfram theory of statements, I shall accordingly take for granted this view of definite descriptions.[2]

We are now in a position to examine the Quinean objection based on referential opacity in modal contexts.  This starts from the assumption that a sentence expresses a necessary truth if and only if it is analytic (Quine 1953 p.143; 1960 pp.195-6).  Of course Quine has well-known reservations about analyticity, but in this context he is prepared for the sake of the argument to go along with the judgements of analyticity which he assumes would be acceptable to those who are happy with the notion.  On this basis he observes that of the following two sentences, the first would generally be judged to be analytic, whereas the second would not:

            (3)        Nine is greater than seven.

            (4)        The number of the planets is greater than seven.

Now if we take the statement expressed by a sentence to be the primary bearer of truth and hence of necessary truth (since to be necessarily true is simply to be true of necessity), and if we take analyticity of expression to be the criterion of necessary truth, then it seems to follow that the statement expressed by (3) is necessary, whereas the statement expressed by (4) is contingent.  But since on the Strawsonian account (3) and (4) express the very same statement, we are apparently left with an intolerable paradox.

---

[1]It is worth noting that the original target of Quine’s Necessity Argument is the notion of a ‘purely referential’ expression (‘Reference and Modality’, in Quine 1953, p.140), though because of this intimate connection Wolfram is right to see the argument as equally threatening to the Strawsonian statement.

[2]For detailed argument against Russell’s theory of descriptions, see Millican (1990) pp.169-80.  Later in that paper, however, I indicate reasons for doubting whether a clear line can be drawn between a definite description’s referring and describing roles.'