This will ramble a bit. I added to this in bits and pieces during the day, and now I'm sleepy. This is a continuation of the earlier discussion about Intelligent Aliens.
You are what you eat!
Aristotle famously compared knowing to eating. In both cases, the organism takes in something outside of itself and makes it part of itself. In eating, say, an apple, the form of the apple is lost and the matter is incorporated into the eater's matter. But with knowing, it is the form we retain and not the matter. That is, when we know a tree, branches of wood do not appear in our brain. [If that were the case, we would instantly stop knowing things, since a wooden head is notoriously impervious to knowledge. That raises the intriguing SFnal possibility of a Know-One-Time organism. I don't know what you could do with one; but there it is.]
Instead, what we retain is the form of the tree, or [more deeply] its essence.
The merest form of knowing is sensation.
Do plants know things? They will "grow toward the sunlight," if they are the right sort of plant. Their roots will seek out moisture, if they are the right sort of roots. But we usually do not consider mere sensation as "knowing." A sodium atom "knows" a chlorine atom [and will bond with it to form salt, if the external conditions are right.] Our heliotropic, hydrophilic plant is a bit smarter than a salt crystal, but we can't say that it "knows" sunlight and water. It is more like it "eats" sunlight and water. It is analogous to knowing, but is not knowing in itself.
So can there be intelligent vegetative aliens?
So, are animals intelligent?
That's a trick question, because "intelligent" can mean many different things, and depending on the need of the argument, we can shift from one to another.
The short answer is that no, animals are not intelligent. The long answer is that yes, they are. The meandering answer is that they are intelligent, but so what? Animals are clearly more cognizant of their surroundings than are plants. Even dimwit cockroaches are one up on petunias in that regard. And dogs got it all over cockroaches. But generalize a concept like "intelligent" broadly enough, and everything is the same thing. "Intelligent" has been used to mean "alert to one's surroundings," "clever at solving problems," "highly trainable," etc. [One seldom sees its root meaning: inter legere, "to read between (the lines)."] But the devil is in the details. The Cat in the Hat is not really the same thing as Don Quixote, despite common membership in the genus, "books." In the same manner, that a flatworm can be conditioned to run a maze does not make the flatworm "intelligent."
However, animals have intention over and above the tropisms of plants, let alone the externally motivated motions of chemicals. That is, when an animal sees something, it sees more than merely the sense information: color, shape, location -- or sound, texture, taste, etc. Or sonar echo. Or heat signature. Don't think we have all the senses possible. Different critters have "made sense" of a variety of things. [But neither does the ability to sense on an additional channel mean the animal is "smarter."]
The senses are prior to motion because they trigger the sensitive appetites, or e-motions. Sensory data is combined into a single ymago courtesy of the "common sense." [The phrase's original meaning.] It can be stored in memory and recalled and even manipulated by the imagination proper. These "inner senses" are often called collectively the imagination.
Now, when a beaver looks at a tree, it sees more than the color or the height or the texture. It sees building material or food [depending on the kind of tree]. And so it moves toward it. When it sees a wolf, it sees more than the sensory, the size and motion and shape. It sees a predator, and so it moves away. If animals saw nothing but sense impressions, they wouldn't move toward or away from anything in particular more so than anything else. Birds do not build nests by gathering Stuff encountered randomly. The bird has a definite intention with respect to the nest.
Chastek calls this "Ptolemaic knowing," because what the animal knows is "essentially related" to the knower "as an absolute center." Objects are known as food/prey, mates, building materials, predators, and so on.
A fly in the ointment, or not
John Wright commented elsewhere and for a different purpose: "I have heard that a frog’s eye is so evolved that if it sees the motion in the air matching the profile of a fly, it will react, but that other motions will trigger no reaction. It is not that the frog sees the other motions and ignores them: no nerve impulse travels from the eye to the brain to begin with. The frog literally cannot see the motions of insects that are not food to it. Its nervous system is programmed and locked only to react to certain stimuli."
Likewise, I have heard that certain small animals will go evasive if they spot the silhouette of a predator bird in the sky; but will react not at all to a bird that eats something other than them. Do they see-and-ignore? Or do they literally not-see?
So what about aliens who do not-see objects outside their templates. Like us. They do not ignore the visiting humans. They agnore them, a term I have just made up.
Ptolemaic knowing + good imagination = behavior with a remarkable similarity to intelligent behavior.
Some animals, like dolphins, chimps, and the like are extemely trainable and clever at problem solving. A chimp can be trained to press numbers from 1 to 9 in the proper order, even when they are arrayed at random on a computer screen and even if given only a glance at them before the buttons are blanked out. But this requires nothing more than sensation [recognizing the numeral shapes], memory [of the locations] and imagination [doing this is a way of getting food]. It does not mean the chimp is "counting" or that it "knows" the number system. Clever engineers have built a robot that remarkably well imitates a cockroach; but a mechanical chimp is more than can be handled. Cockroaches are way down there near the plants: they sense, but do not know. Chimps are at the other end. They know something.
The SFnal applications are obvious. The old conundrum: how do we know if the aliens are intelligent beings? Here is where we can play games with the word "intelligence," by redefining it to mean whatever it is that we see. A familiar SF trope is the alien we fail to recognize as intelligent [and then learn better and become humble]. Less common is the story in which a firm belief in the intelligence of the alien is dashed by the realization that it is only a clever and eminently trainable animal.
So where do humans come in?
Discussion of this sort of thing oft overlook the fact that humans are a particular animal, and therefore everything we just said about animals goes for humans, too. I once wrote a story, "From the Corner of the Eye," about a human's encounter with a species that had so perfected mimicry as to go unnoticed by humans, because they were once our natural prey. If ever we do spot one, well, we learn what predators do when they spot a prey while hungry.
So we can look at something and see “food.” But we can also look at it and see “beans” or “beef.” As Chastek put it, "A bird can see something on the ground and see 'house part'; we can look at the same thing and see 'twig.'" This is non-Ptolemaic knowing. We need not grasp a thing solely as it relates to us. It's not just "house part," it's lumber, it's a two-by-four, it's wood, it's dry, seasoned, it's $241/1000 board feet... A host of things. We can consider the object without privileging a particular reference frame. Call this "Einsteinian knowing."
The human can grasp things as they are, and not merely as they are in relation to himself. (And, by the way, note the prehensile connotations of "grasping" as knowing.) This brings in a whole different order of "intentionality" than even the higher animals.
Intelligent vs intellectual
With the term "intelligent" poisoned by notions of cleverness, problem-solving, trainability, et al., perhaps we should use the term "intellection" instead for this capacity of grasping the DIng an Sich. The intellect deals in conceptions, not merely perceptions; in universals rather than particulars; in "dogs" rather than Fido or Spot or Rover. It forms concepts by a) reflecting on the percepts that the senses have provided and b) abstracting their essences. This is the nature of science: to know.
Just as the sensitive appetites (e-motions) act to move animals toward or away from sensory objects (perceptions), so too does the intellective appetite (volition) act to move intelligent beings toward or away from intellective objects (conceptions). This is the nature of art: know-how.
The greater the abstraction, the less imaginable it becomes. Try to imagine "dog." It cannot be done. You will inevitably imagine a particular dog - Fido, or Spot - or at the very most, a particular kind of dog: an afghan, a boxer, a shar-pei, or whatever. (And even within breeds they are not exactly alike, and so....) The problem gets worse when you try to imagine a canine, let alone a canid (includes foxes and dogs) or caniforma (includes bears and seals and dogs) or carnivora (includes cats and dogs). You get the picture. Or rather, you don't. We can conceive of these things; but we cannot imagine them. Still other products of the intellect lack any sort of material being: justice, love, power, beauty, etc. When you imagine beauty, what do you see? the Parthenon? a perfect rose? the vista of the Sangre de Cristo mountains? J-Lo? But I digress.
So how do we know we have discovered "intellective" intelligence and not merely "perceptive" intelligence?
Clever and trainable can look a lot like intelligence. And the training can be done by nature in the same fashion that nature can "select." Mack Reynolds once wrote a short novel - Beehive - that involved an encounter with humanoid aliens that were not actually "thinking" but only operated by instinct. The story had some difficulties because the notion of "instinct" was Cartesian [and therefore wrong] rather than Aristotelian [and therefore right]. But it was an interesting attempt.
Language will do it. How to recognize a language is another matter. When a beaver spots a wolf, it will dive underwater and make for its lodge. In doing so, its natural swimming motions will slap the water with its tail and all the other beavers hearing it will likewise dive. Now here's the thing. Seeing this [or hearing it] and being intelligent, we cannot help but think the first beaver has warned the others. After all, it's what we would do in that situation. But that shows that intelligence may not be all it's cracked up to be. By projecting human intellection onto the beaver, we fool ourselves into thinking that we have seen intelligent behavior and "communication." [Communication: a much overworked term. You can communicate a disease. That ain't "talking."] Well, no one ever said intelligent = correct. In fact, the beaver is simply reacting to a perception of a predator and doing what Darwin formed it to do. Beavers who did not do this had a way of leaving the gene pool. All the other beavers reacted to the characteristic noise. Those beavers who did not so react did not leave many offspring. So it looks like one beaver "told" the others when nothing of the sort has happened.
A language is not a set of signs for things, but a system of grammar and relations. But see Juliette Wade for language neep. This goes beyond the present essay. (Yes, some digressions even I will eschew.)
Other signs are art (the caves of Lascaux will do), speculative philosophy, abstract mathematics, law codes [and not merely lawful behavior], science, literature... These are all useful markers. Many of them presuppose language; and many of them have the same how-do-you-know-it-when-you've-seen-it problem.
But by now we have enough problems for our intrepid SF heroes.