The Master Argument appears in one format in Three Dialogues as a discussion between Philonous and Hylas as to whether Hylas can conceive of a mind independent object. It is when Philonous points out that by conceiving of such an object, Hylas is necessarily framing the idea within his mind that Hylas admits that he has nothing but left but certain “scruples” in his defence against immaterialism. At first glance, the idea of conceiving of a mind independent object does indeed seem contradictory and initially one maybe as easily persuaded by Philonous’ challenge as Hylas is. However, it does not take long to realise that Berkley appears to have not been careful with his choice of words and has committed various conflations leading to fallacies of ambiguity. It is my view that these fallacies play a large role in undermining the success of the Master Argument. In order to analyse the strength of what Berkeley saw as his most convincing argument against the existence of mind independent objects I intend to look specifically at Bertrand Russell’s discussion of the Master Argument in his evaluation of idealism in his book The Problems of Philosophy. I will then look into the nominalist interpretation of the Master Argument in order to see if Russell’s allegations can be sidestepped once we discern the assumptions that Berkeley arguably based the Master Argument on.
The Master Argument was originally known as the inconceivability argument until Andre Gallois referred to it as the former in his 1974 article as a nod to the prominence that Berkeley gives it within his attack on materialism. It appears in both Principles of Human Understanding and Three Dialogues in slightly different versions but the argument is essentially a call for Berkeley’s readers to partake in a thought experiment in order to prove the contradictory nature of the belief that objects can exist independently of being perceived by a “spirit” (the term that Berkeley uses for active mental beings, namely humans and God). What Berkeley is claiming here is that sense data (ideas in Berkeleian terms) are the only things that we can have certain knowledge of and as sense data depends on our perception of sensible qualities, it must exist solely within our minds. Berkeley concludes this line of thought by stating that as mind dependent sense data are the only things whose existence we can be certain of, everything that we can know of reality must necessarily exist in some kind of mind(s). The Master Argument is an attempt to explain and support this argument through the reader using their own experience (the base of all knowledge for Berkeley as an empiricist) to come to the realisation that existence outside of the mind is inconceivable.
Bertrand Russell in his chapter on idealism in The Problems of Philosophy points out both a conflation and a tautology in Berkeley’s argument against the existence of mind independent objects. Russell highlights what he sees as the “ultimate fallacy” by stating that Berkley is guilty of conflating what is apprehended with the act of apprehension itself while referring to them both as an idea. The act of apprehension is clearly an activity in the mind, whereas there is little evidence that the object being apprehended is also mind dependent. Russell supports the invalidity of Berkeley’s conflation by arguing that the mind’s ability to acquaint itself with things other than itself is the primary characteristic of the mind and the process by which we acquire knowledge. Therefore to say that all things known to us must necessarily be in the mind is seriously limits the mind’s power of knowing. Russell then states that Berkeley’s argument also includes a tautology if what we mean by an object being in the mind is the same as being apprehended by the mind, and if this is the case the object may not be mental. Russell then concludes by claiming that he has proven that Berkeley’s argument is “wrong in substance as well as in form, and his grounds for supposing that ‘idea’-I.e. the objects apprehended – must by mental, are found to have no validity whatever.” 
In his book Berkeley, George Pitcher gives a good analogous example than can be used to clarify the tautology that Russell is referring to. Pitcher gives an account of a man who argues that it is not possible to stage a play about Robin Crusoe and his time alone on a desert island as the character in the play would not be alone because he is in front of an audience. Pitcher points out that this claim is “obviously absurd”  because the presence of the audience has no relevance to Robinson Crusoe’s solitariness as he is not anywhere near the stage, it is the actor who is portraying him who is being observed by others. And so, just like the man attempting to refute that it is possible to have a play about Robison Crusoe alone on an Island by using a point that is only applicable to Robinson Crusoe the character, Berkeley is refuting the claim that there are unperceived objects by using what is only applicable to the act of apprehension and not to the object being apprehended.
Berkeley was undoubtedly a very astute and proficient philosopher who saw himself as the defender of common sense in the face of doubt-inducing and far-fetched theories (something that may seem ironic in light of the section above). It is then fair to say he must have truly believed that the Master Argument was supported by strong foundations in order to place so much faith in it. This is essentially what numerous philosophers have argued and so it is important to look at suggestions as to what these foundations before the Master Argument is dismissed as unequivocally fallacious.
The foundations that I believe are the most supportive of the Master Argument are to be found in nominalist interpretation’s such as Thomas Lennon’s, due to the connection it highlights between Berkeley’s attack against materialism, his rejection of abstract ideas and his views on language  . The doctrine of nominalism can be reduced to the view that there although there are general terms, there are no general ideas, only particulars. For example, when we conceive of a chair we cannot conceive of a general idea of a chair as we always picture a specific chair with uniquely distinguishable qualities. This is a possible interpretation as Berkeley likens ideas to images in that they are necessarily in the mind and necessarily particulars. This also fits with Berkeley rejection of abstractionism as he believes that sensible qualities cannot be abstracted from an idea because the image of the object would be incomplete. If this is the case then Berkeley was in part founding the Master Argument on the argument that there can be no abstract ideas of an object, and no qualities of an object can be abstracted from it. The Nominalist view therefore sidesteps the fallacy demonstrated in Russell and Pitcher’s argument because if there are no general or abstract ideas of objects, the sensible qualities (ideas for Berkeley and sense data for Russell) of the object we are conceiving of can only exist when being perceived as a quality of a particular object. This means that the act of perceiving and the object being perceived do have some kind of necessary connection, leading to Berkeley’s conflation. With regards to the tautology between the object and the representation of the object, Berkeley sees the image of the object as the object itself and so all of their qualities must correspond.
From my discussion of the Master Argument it seems to me that it cannot be seen as a successful argument against mind independent objects. The ambiguity of Berkeley’s language does him a disservice in that one cannot attempt to validate or clarify his argument without bringing to light various fallacies that weaken the argument’s structure. This is particularly damaging to the Master Argument considering the counter intuitive content. Of what I can take from the nominalist interpretation of the Master Argument, the meanings of the ambiguous words used may lie in the