[1]
However, some very interesting and very recent (currently unpublished) work by Susan Carey calls into question the interpretation of some of the extant pro-propositional attitude empirical work.
[2]

Davidson equates thought with propositional attitudes. He famously expresses his denial of propositional attitudes to nonhuman animals as the claim that animals can’t think. See Davidson (2001a). Here I focus upon arguments found in his 1975 paper “Thought and Talk”, and his later paper “Rational Animals”.

[3]
Another reason for focusing on P1 rather than is that finding counterexamples to P2 will at most make room to usher specific species into the thought-capable fold, but will not challenge Davidson's argument directly.
[4]
Some have argued that there is no account of what a proposition is that is both coherent and satisfies the various criteria that propositions are traditionally supposed to satisfy (that tradition stemming initially from Frege). See e.g., Dennett (1987a), and Churchland (1981). It is unfortunate, but true, that if our notion of a proposition is fundamentally incoherent, and no compromises can be reached on the criteria propositions must satisfy, then there is no such thing as a proposition. A fortiori, we can’t stand in any meaningful relation to propositions, so we lack propositional attitudes. Such is the position of some eliminativists. Others have compromised on the demands put on propositions. Quine, for instance, while being no friend of abstract entities such as propositions as usually conceived, found sentences to be less ontologically troublesome stand-ins for them, and held that to have a propositional attitude is to stand in some relevant relation to an eternal sentence—thereby still satisfying our philosophical intuitions about the role of propositional attitudes in explanations of human thought and behavior.
[5]

In the literature, “interpretationism” is often used interchangeably with “interpretivism”. Since “interpretivism” is more commonly used to denote a strategy of legal interpretation, I will use “interpretationism” here.

[6]

Decision theory, for instance, gives us one model of rationality. Interestingly, in many ecological studies of foraging behavior that use decision theory to assess animal choice, animal behavior is found not to just be adaptive, but optimal. For example, animal foraging decisions approach optimality. See e.g., Stephens & Krebs (1986).

[7]
The debate about propositional attitudes, language, and capacity for thought has implications beyond philosophy of mind to ethics. As Davidson himself noted, personal and sub personal levels of description refer to different logical subjects, and thus  Davidson’s argument has implications for the possibility of attributing personhood to animals. See again, http://www.projetogap.org.br/en/.
[8]
Substitution of co-reffering terms in “opaque” contexts may not preserve truth. Such is the case with propositional attitudes. Thus, while it is true that Lois Lane believes “Superman is a hero”, it may be false that she believes “Clark Kent is a hero”, despite the fact that Clark Kent is identical to Superman.
[9]
Davidson nowhere presents his Master Argument in this precise form. I reconstruct the logical form of his argument from “Thought and Talk” and “Rational Animals”.
[10]

This ought to be distinguished from the idea that having propositional thought requires having some concepts, and that the contents that can be entertained by a creature in propositional thought are constrained by the set of concepts that the creature possesses. This view, held by a variety of thinkers from Frege to Fodor, stems from the belief that the propositions to which a thinker stands in relation in having a propositional attitude are complex entities composed of concepts. But then the question of whether animals have propositional thought can be recast as the question of whether animals have concepts. If, additionally, one combined this view of the cognitive structure of propositions with a view according to which concept possession requires language, one would have an argument for why language is necessary for propositional thought. However, whether concept possession requires language is a question that depends, among other things, on what concepts are. Whether the vehicles of thought are language-like, as I argued earlier, is orthogonal to the issue of whether an organism possesses the capacity to speak or understand speech. Therefore Davidson’s argument cannot rest on the nature of concepts.

[11]
Kristen Andrews takes autistic subjects to be counterexamples to Davidson’s view, which would also argue against M2. (Andrews 2002).
[12]
In addition, at ages far younger than those at which children pass the false-belief task, they act as interpreters, in Davidson’s sense. Any parent knows that their children interpret speech well before they are speakers, and long before the age at which they pass the false-belief task. So if interpretation is central to having propositional attitudes, it doesn’t require a robust theory of mind.
[13]
Of course, Onishi and Baillergeon’s interpretation is subject to refutation. Should their findings (they developed a nonverbal task that suggest that infants much younger than previously supposed represent others' mental states, such as goals, perceptions and beliefs.) reflect something like proto-beliefs rather than full-blown propositional attitude-sustaining beliefs, M3 would not be falsified.
[14]

We ought to reject this interpretation for the purposes of Davidson’s argument, despite the fact that we may ultimately agree with it as a necessary condition for having propositional thought.