1) The document proposes a biological definition of self grounded in evolution and the origins of life. It defines self as a propensity of a replicator to protect the boundaries containing its replicating machinery. 2) The earliest self was a self-replicating nucleotide sequence that had a high probability of replicating its own sequence. More complex life forms developed barriers between their replicating machinery and the environment. 3) Very complex life, like humans, have multiple boundaries and changing aspects to their self but also central tendencies that remain constant and drive survival and replication. This biological view of self provides a useful framework for studying consciousness.

1. Aaron Blaisdell 01/28/09 1
A Biological Definition of Self
Psychology as a science grew out of a branch of philosophy concerned with
understanding the mind. William James' Principles of Psychology (1890) defined psychology as
the study of Mental Life, which includes feelings, desires, reasoning, cognition, etc. These
phenomena could be studied by collecting data through verbal report and introspection. James
was not so concerned with the validity of these types of data as a "window" into consciousness.
He decided to leave the metaphysical question "what is consciousness?" to the philosophers.
Though James realized that the problem was not solved by sweeping it under the carpet, he
wished to put off empirical investigation of such metaphysical musings until a future date. By
the beginning of the following century, empirical psychologists went even further than James in
claiming that consciousness and mental life could not be investigated scientifically at all.
Rather, they claimed that overt behavior provided the only phenomena that could be objectively
studied, and that our theoretical interpretations should be concerned only with the explanation of
such behavior.
However, with the renewed interest in cognition in humans and animals beginning in the
1930s and 1940s with Tolman in learning theory and Koehler and (later) Gibson in Gestalt
psychology, the study of mental life in general, and consciousness in particular has become
fashionable again. The reason for this reintroduction of consciousness was not due to the
abandonment of behaviorism, but from relaxing the strict constraints initially imposed by the
early behaviorists on the investigation of observable behavior. We still agree that overt
(including muscular, verbal, neuronal, sensory, etc.) behavior provides us with the only data
from which to construct and test psychological theories; however, we can infer intervening
variables or hypothetical constructs that are presumed to mediate input to output such that we
can explain large sets of data with few variables, and can make predictions regarding the effects
of intended manipulations.

2. Aaron Blaisdell 01/28/09 2
With the return of consciousness to the scientific playing field, more than ever our
understanding of what consciousness is or even how to study it is impeded by a good definition
(even operational) of consciousness. I am not going to attempt a definition of consciousness
here; rather I will attempt to provide a useful definition of what a “self” is. The reason I have
chosen to work on the problem of self is because such a concept is integral to any definition of
consciousness, which is currently tightly linked in both philosophy and psychology to the idea of
intentions. To take an intentional stance (i.e., to attribute intentions or rational goals to oneself
or others) implies a concept of self and, for higher-order intentional systems, other selves from
the standpoint of the observer taking the intentional stance.
I will attempt to show the usefulness of defining self from a biological perspective and
how such a concept may illuminate how we should think about consciousness. I must first be
up front in stating that I am a physical monist, and that I believe our senses are a filtered
window into a single "real world" (though perceptions may be potentially infinitely variable) of
which anything can be explained in terms of matter, energy, and their interaction. Accepting
these assumptions, we must define self (and consciousness and, ultimately, phenomenology)
within these constraints. I am going to ground the biological definition of self in the process of
evolution by natural selection (Darwin, 1859) and the origin of life.
Imagine the origin of the very first nucleotide sequences that were able to replicate.
There are many possible ways for such an event to occur. The replicating nucleotide sequence
(hereafter called "replicators") need only replicate that part of its physical structure necessary to
produce more replicators. That is, replicator A could just replicate its molecular machinery such
that the products of replication, B and C, have the potential to themselves replicate. However,
this machinery is subject to degradation due to environmental factors, such as the medium in
which the replicator resides, energy entering the medium from outside (e.g., radiation), the
decay or errors of the elements and molecules making up the replicator, and other chemical
reactions, etc. Now let's imagine a replicator that not only replicates the machinery necessary

3. Aaron Blaisdell 01/28/09 3
for replication, but also machinery that is capable of producing substances (e.g., proteins) that
increase the integrity and constitution of the replicator (i.e., reduce the rate or probability of
degradation and protect it from disruptive environmental factors). For example, a protective
coating in which the replicator is housed (e.g., a membrane around the nucleic acids) would
reduce the corrosive effects of the environment on the nucleotide sequence. However, the
protective coating itself is subject to wear and tear; thus, the newly housed replicator could
evolve repair machinery that would repair damaging alterations to the protective coating. It
should be noted that such repair machinery could evolve that would repair deleterious
alterations (i.e., mutations) to the nucleotide sequence. Such machinery does in fact exist (see
Sinha & Hader, 2002, for a review).
We now have, in this historical hypothesis, a replicating machine that is well on its way
to becoming the recognizable beasts (plant, animal, bacteria, etc.) that we call life. Many
biologists would list replication as one of the defining properties of life. I would go even further
in claiming that replication is perhaps the defining feature of life. I must emphasize that this
definition of life precludes our drawing any absolute boundaries between life and non-life.
Rather, the varieties of life can be thought of as existing along a continuum upon which we
arbitrarily make relative distinctions between non-life and life. This allows us to call beavers and
clams life, and ice crystals (which exist only transiently under certain conditions) and photocopy
machines (which depend upon design by the sky-hook of human intention) non-life. However,
recognize that these are fundamentally arbitrary distinctions, because life as we know it is also
transient, exists only under certain conditions, and is entirely mechanical in physical nature and
processing (under my starting assumptions).
It has become clear through the preceding discussion that replicators probably started
out as relatively simple things and became more and more complex through the workings of
natural selection continually shaping replicator phenotypes (and their transmission) generation
after generation. After roughly 3.5 billion years we have humans along with a myriad of other

4. Aaron Blaisdell 01/28/09 4
life forms on this planet, some of which claim to be conscious and to have selves. So what are
these selves? Was there a transition point or threshold reached during evolution where the first
self evolved and started producing new selves? Not at all! In the view I have been
constructing, I am trying to show that a self is a property of life that is defined by the replicator's
ultimate objective, that is, replication. What does the replicator want to replicate? The most
obvious answer is: "Itself"! But can we define self without resorting in circular fashion to the
term self? I think so. From our biological perspective, self is a propensity (conscious or non-
conscious) of a replicator to protect a boundary within which the replicating machinery is
contained. (For each individual, there exist many boundaries at many levels, of which the
replicator has a keen [self] interest in monitoring, modulating, and protecting.) Thus, the
simplest self is a piece of replicating machinery, such as the first nucleotide sequences to ever
replicate. These nucleotide sequences had selves (using our definition) because the product of
replication was essentially identical to the initial replicator. That is, a successful replicator didn't
replicate just any nucleotide sequence (like a random number generator), but had an extremely
high probability of replicating its own nucleotide sequence (i.e., it maintained construct validity or
a central tendency). I believe that this statistical and biological sense of self is the best
empirical way to define what self is. More complex selves began replicating "themselves" (allow
me some teleological language, since it is clear that I do not imply actual teleology, but talk in
merely descriptive "as if" terms) and constructing barriers between the nucleotide machinery
and the medium in which the nucleotide sequence existed (usually such barriers are selectively
permeable to stuff in the medium to the benefit of the replicator). Very complex selves such as
eukaryotes, not only replicate "themselves" and construct selectively permeable barriers around
"themselves", but also set up barriers around barriers each which selectively allows different
molecules to pass through them. Incredibly complex selves, such as arthropods and
vertebrates construct barriers that they "themselves" can cross over, but that are defined as part
of their self because they will defend it from other selves (i.e., other replicators). A bird will

5. Aaron Blaisdell 01/28/09 5
sometimes protect its territory from some intruders (predators, competitors, etc). Finally,
humans (at least) have selves that change over time (e.g., epithelial tissue, clothing, girlfriends),
but that also have many central tendencies that remain relatively constant across the lifetime of
the self (e.g., teeth, social security numbers, offspring, and the goals of survival and replication).
Grounded in biology, the idea of self, although much more loosely defined than many
philosophers or scientists would like, becomes a very useful concept. It frees us from the
constraints under which previous attempts to define consciousness were made. We now have
an understanding that there is no single "point" at which a thought, idea, feeling, perception, or
sensation enters into consciousness or awareness (see Dennett, 1991). We have a much
clearer idea, when taking the intentional stance, of who the intender is or how we should define
the intender. And most important, we can construct an operational definition of self for the
purpose of empirical investigation, based on observable responses elicited and emitted by the
subject who's "self" we wish to define (with the full understanding that there can be many
selves, depending on how we wish to measure them, or what responses we are interested in
observing. This becomes most apparent with split brain patients, but also exists at many subtler
levels in "normal" individuals). For example, we can ask: What is the individual willing to
defend? We can probe its boundaries by exploring were it will and will not permit us to invade.
And to connect more closely with the investigation of consciousness, we can ask what kinds of
cognitive systems have evolved to monitor self, and what are they designed to protect or
pursue? (This last question is directly analogous to the way immunologists study the evolution,
functioning, and comparative distribution of immune systems.) While the definition of self I have
attempted to construct is not definitive, it provides a foothold on which arguments and
experiments can be made. Even if we ultimately reject the above definition, it will have had
heuristic value in furthering our search for self.