Before reconstructing Descartes’ Trademark Argument (TA), I’ll first describe the distinction between formal reality and objective reality. Formal reality is the kind of reality that any actually existing thing has; furthermore, it is the kind of reality that an infinite being would have more of than a finite being. Objective reality, on the other hand, is the kind of reality that only ideas can have. Furthermore, roughly speaking, an idea’s objective reality is the amount of formal reality that the idea’s object would have if this object actually existed. An idea’s object is the thing, whether actually existing or not, represented by the idea. Descartes’ TA is as follows. I have an idea of God as an infinite, perfect being who created me. This idea has the most objective reality that an idea can have. Furthermore, as all things must necessarily have causes, this idea of God must necessarily have some cause. But the Reality Principle is clearly true—there must necessarily be at least as much formal reality in the cause as [i] there is formal reality in the effect if the effect is an actually existing thing, or [ii] there is objective reality in the effect if the effect is an idea. Hence, the Reality Principle implies that my idea of God must be caused by something that has at least as much formal reality as the idea of God has objective reality; but this idea has as much objective reality as an idea can have. Only God, however, could have enough formal reality to cause my idea of God. Hence, God actually exists; God has formal reality. Furthermore, God created me, since my idea of God included his creating me. Also, God is a perfect being, since my idea of God included his being perfect. And since God is perfect, he is no deceiver. If God created me such that it was logically possible for my clear and distinct ideas to be false, then God would be a deceiver. Therefore, by modus tollens, it is not logically possible for my clear and distinct ideas to be false.
The Cartesian Circle Objection to Descartes’ TA is as follows. All of the premises, which include all the argument’s propositions except its final conclusion, either are clear and distinct ideas or are derived from clear and distinct ideas. Hence, in order to legitimately use these premises in a deductive argument such as Descartes’ TA, one must presuppose that one’s clear and distinct ideas cannot be false; one cannot deny or even doubt the argument’s conclusion if one is to be (rationally) persuaded by the argument. Hence, the argument’s conclusion is an implicit premise in the argument itself. Therefore, Descartes’ TA is question-begging.
My objection to Descartes’ TA consists of two parts. First, I parody the TA in such a way as to show that premises analogous to and just as plausible as those used in the argument imply the existence of a maximally malevolent and omnipotent being; I will call this being the super-devil. Second, I argue that  their coexistence causes it to be logically possible for my clear and distinct ideas to be false—this is the negation of the TA’s final conclusion. My parody, briefly put, is as follows. I have an idea of the super-devil, who is infinite, omnipotent, and maximally malevolent. This idea has an amount of objective reality comparable to that which the idea of God has. This idea must have a cause. By the Reality Principle, this cause must have as much formal reality as the idea of the super-devil has objective reality. However, only the super-devil, who is omnipotent and maximally malevolent, could be the cause of this idea; God cannot be the cause, since God is not malevolent. Hence, the super-devil actually exists. Now, let’s move on to the second phase of my objection. Suppose, for the sake of argument, that [A] Descartes’ TA succeeds in demonstrating God’s existence. (I’ll ignore the TA’s final conclusion for now.) [B] But if the TA succeeds in proving God’s existence, then my parody proves the super-devil’s existence. However, both God and the super-devil are omnipotent; this means that both of these beings have every power and ability. Even if we ignore the justified worry that it seems logically impossible for two omnipotent beings to coexist (each being would depend on the other for its own existence), I still contend that the super-devil’s existence makes dubious the TA’s conclusion. The super-devil is omnipotent and maximally malevolent; hence, he is a deceiver and does what is in his power to cause my clear and distinct ideas to be false. Hence, the super-devil and God clash over whether or not my clear and distinct ideas correspond to truths. Since both God and the super-devil are omnipotent, it is not obvious what the exact result of this conflict would be. However, surely it is logically possible for the super-devil, who is omnipotent like God, to successfully cause some of my clear and distinct beliefs to be false. In which case, the conclusion of the TA would be false; so one of argument’s premises would also have to be false. But then the TA would be unsound. The only two ways to avoid this objection are to deny my parody argument’s soundness or to deny that the super-devil’s omnipotence is equal to that of God’s. However, the former requires a denial of the TA’s soundness, since my parody’s premises are equally as plausible as the TA’s premises. Furthermore, the latter way out seems prima facie false, since the super-devil would not be omnipotent in the first place if God had more power than the super-devil; yet we’ve supposed that the super-devil, who is omnipotent, actually exists. So, even if we suppose that the Trademark Argument successfully demonstrates God’s existence, then it also implies that, contra its own final conclusion, my clear and distinct beliefs might be false. Therefore, since [A] and [B] imply , Descartes’ TA is somehow unsound.