There are a few possible sources we could peruse for the purposes of uncovering the nature of canine souls. We have chosen to look at Aristotle and his treatment of the soul within De Anima.
Artie defines a soul as…
… the first actuality of an organic body that is potentially alive
 
Let that swirl around your mind for a bit; taste it as if it were a fine wine. Once you’ve done that, feel free to say to yourself…
‘um… what?’
What does Aristotle even mean by that? Perhaps what we should go over first is what he doesn’t mean.
Aristotle, although undeniably influenced by his mentor, departs rather dramatically from Plato’s conception of the soul. Plato believed that the soul was an object of sorts, trapped within the body. It is a very real thing that resides within in us, until the day of our death when the soul escapes back into the world of the forms where it regains infinite knowledge and wisdom.
Aristotle believed that such a notion was unnecessary. Despite how difficult it may sound, the soul can be explained through logical, empirical means.
Matter and Form
Aristotle believed that any object insofar as it is an object can be explained by two criterion.
  1. Matter: the material the thing is made of
  2. Form: the meaningful arrangement of said matter
If we were to examine a bronze statue of an ancient hero, we would very simply say that its substance, the stuff it is made out of, is bronze. The form of the statue is the meaningful arrangements of its parts. The statue has purposeful shape and structure. This shape and structure happens to resemble a Greek hero. If you were to combine these two (matter and form) then you would have a complete picture of the object in question.
Aristotle believed that substance was potentiality. Bronze insofar as it is bronze, has the potential to be a statue of a hero. It is only when the substance takes on a meaningful form (a Greek hero) that the object is actualized. Simply put…
Matter is potentiality, and form is actuality…” -Aristotle (De Anima)
 
Similarly the human body is composed of matter. In this way it has potentiality. It would follow then that the soul is the actuality of the body. The soul gives meaningful purpose and shape to life. the combination of matter and form create a recognizable human life. And so we see that the soul is the first actuality of a body that is potentially alive.
All make sense so far?
Don’t bother answering that, we’ve still got much to cover.
The three types of souls
It is important to keep in mind that the soul according to Aristotle is not an object in the way that Plato imagined. Rather, it is a grounding principle of sorts. It is the realization of life. The soul is the one thing that enables a body to engage in the necessary activities of life. And interestingly enough, there are several parts of the soul. They are the nutritive soul, the sensible soul, and the rational soul.
1. The Nutritive Soul
The soul is that by virtue of which things have life. The first part of the soul is known as the nutritive part. This is the first and most widely shared among all living things. For it can be said that anything that takes in nutrition, grows from this nutrition, and eventually decays over time has a soul.
plant
This part of the soul can be found in humans, animals, and plants. It was believed by Aristotle that the nutritive part of the soul aims at the continuation of life. It is impossible for any one thing to exist eternally and without decay.
However, it is possible for life, through virtue of the nutritive soul, to regenerate in the form of offspring. The continuation of life is the final aim for nature. Any creature with a nutritive soul will therefore be inclined to strive towards this end.
It is interesting to note that plants have only the nutritive soul. Plants have no higher aim other than the continuation of life. The nutritive soul allows plants to take in nourishment, grow, and spread life. However, their role in nature stops there.
2. The Sensible Soul
The sensible soul, or the soul of perception, is the part of the soul that by virtue of which we are able to perceive. In addition to sensation, the sensible soul endows us with the ability to retain memories, perceive pain and pleasure, and have appetites and desires.
While plants do not possess the sensible soul, animals and humans most certainly do. Aristotle makes a point to clarify that not all animals have the same abilities of perception. While some creatures have all five senses (sight, hearing, smell, taste touch,) some creatures are only endowed with the sense of touch. Animals that do not possess the proper sense organs (some insects for instance) will not have the proper potentiality for perception and therefore can not be actualized by the sensible soul.
dog
Ancient mosaic of a classical dog
All animals have touch. Aristotle classifies this as a default of sorts. Any animals insofar as it is an animal will be able to have the sensation of touch and therefore can be said to possess the sensible soul.
Aristotle also takes the time to mention that any animal that possesses the sensible soul must also possess the capacity for pleasure and pain. The implication to this is that any creature with the sensible soul will therefor also have desires or appetites. Appetite can be said to be the the desire for that which is pleasurable to our senses while simultaneously avoiding that which is painful. It can be said then that animals have passions. They are subsequently driven by these passions toward an end.
Hunger and thirst are forms of desire, hunger a desire for what is dry and hot, thirst a desire for what is cold and moist; flavour is a sort of seasoning added to both. We must later clear up these points, but at present it may be enough to say that all animals that possess the sense of touch have also appetition.

-Aristotle (De Anima)

 
Aristotle believed that animals and humans both possess the sensible soul. However, he asks the question if animals have the capacity for belief. Belief would seem to imply conviction. Conviction would seem to imply that a creature was persuaded, because one can not be convinced of something without being persuaded in some way. Finally, persuasion would seem to imply a rational function of measuring possibilities and drawing conclusions, a function that Aristotle believed animals did not possess.
3. The Rational Soul
While it can be said that plants possess the nutritive soul and that animals possess the nutritive and the sensible soul, the rational soul belongs to man alone. The rational soul is that by virtue of which we possess the capacity for rational thought. A rather daunting notion, Aristotle divides rational thought into two groups.
The first is known as the passive intellect. It is the part of our mind that collects information and stores it for later use. This is almost an extension of the sensible soul in that it allows us to take Aristotle philosopherin that which we perceive, create a belief towards it, and store it for later use.
The active intellect is the part that allows us to engage in the actual process of thinking. We manage to call forth knowledge stored in our passive intellect and shape it into meaningful ideas using the reasoning power of our active intellect. Aristotle also believed that the active intellect was responsible for our ability to consider abstract concepts that we have never perceived. Intellectual abstracts become manageable with the power of our active intellect, philosophy becomes possible.
Actual knowledge is the same as its object; potential knowledge is temporally prior in an individual, but in general it is not even temporally prior. But active intellect does not understand at one time and not at another. Only when it has been separated is it precisely what it is, all by itself. This alone is immortal and everlasting.
I know what you are probably thinking at this point.
Modern science has disproven much of Aristotle’s ideas on the soul. There is no nutritive, sensible, or rational soul. All three levels of the Aristotelian soul can be explained by nutritive and perception organs. And the rational soul is merely the rapid firing of neurons in our brain.
Perhaps…
Perhaps not…
Old Artie didn’t have the modern conveniences that we enjoy today. He did not have thousands of years of medical scientific progress to explain the various functions of life. He was, in a very real way, the guy who was kicking off said medical scientific progress.
The fact that he relied on observable, empirical phenomenon was an enormous step forward. No longer were thinkers restrained to believing in ethereal forms or mysticism to account for the inexplicable occurrence of life.
So…do dogs have souls?
No answers for certain, but we like to think so.