For Dewey, “mind” is an event in nature. An event is an occurrence, a coming to be, a realization of potentiality that produces a change in what exists. Nature is the totality of what is, was, and will be, but also what is possible and the structure of possibilities. Mind is a possibility of nature that designates a particular kind of even that is not special to humans, and perhaps not even in organics. What is mind?
There are two levels of minding for Dewey. First, consciousness or low-level mind is not a thing, substance, or even a discrete self-contained event. Something is “conscious” to the extent that some localized natural complex is capable of mediating its temporal relations within its environment. That is, to the extent that it can anticipate its environment and react in advance. This is not require self-consciousness, and by this definition, plants might be said to have “consciousness.”
I have not said that there is some hidden property of “mind” in all things. Mind is an emergent property of nature, and is possible when anything can anticipate and react in advance. Strictly speaking, since all of nature is continuous, if a plant has consciousness, then why not a rock? Insomuch as we may describe its behavior in terms of expectant laws of nature, which are not taken to be absolutely necessary but strong habits of the cosmos, a rock has mind, but that is a trivial case. What separates rocks from plants and then animals is the ability to mediate one’s own anticipation. An animal can learn. Plants can genetically or chemically adapt. Rocks do not. An implication is that a conscious thing must have some kind of local “memory” as in the case of DNA.
“Mind” proper is just the ability to mediate temporal relations linguistically, i.e., to not only be conscious, but to select how one symbolizes one’s relations with the environment. It’s meta-mediation. Humans can invent and alter the symbolic ways in which we anticipate and plan, whereas a given plant cannot. The prime example of “select how it symbolizes” is to communicate or think in language. Minding beings can represent the semiotic situations in which they are engaged, i.e., how they are involved in the world, and anticipate to a vastly higher degree since they can alter that representation. A plant does not figure out the difference between a grow-lamp and the sun.
I am using “semiotic” in a Peircean manner. Those unfamiliar with Peirce will likely misinterpret the statement about semiotics, because they tend to think of them in linguistic terms. Peirce means us to understand semiosis as the study of relations in general, to put it simply, and he affirms that relations are real.