Gnostic adj. of or relating to knowledge (from gnōstos meaning 'known')
Agnostic adj. a person who believes that nothing is known on some topic, either at the present, or in principle
In the philosophy of religion and recent public debates over atheism, a distinction is made of the difference between believing in God (theism) and not believing in God (atheism), but a third option, agnosticism is often regarded as the equivocation or uncertainty about whether or not there is a God. In fact, agnosticism is the denial that the existence of a God can be known one way or the other, and that we should stick to the facts we do know. Agnostics reject gnosticism of either kind. In biology, there are similar matters to consider.
Comparative biology is a now relatively unpopular (and often thought to be outmoded, replaced by unqualified reliance upon molecular data) approach to the nature and relationships of living things. So, what is knowledge in comparative biology? We are able to observe and therefore know organisms and their parts from fossil and living specimens to some degree through direct acquaintance, under microscopes, or as gels and know something of their behaviour, genetics and ontogeny. We can even see fertilization, cell growth, life cycles and environmental conditions in modern organisms. Knowledge, in comparative biology, is inextricably linked to what we can observe. It is empiricism of the highest order, and relies upon actual observations as the basis for knowledge claims. However, it is what we can predict (rather than observe), which makes comparative biology 'interesting' to the majority of contemporary biologists.
Given the hypothesis-driven emphasis in of 21st century comparative biology, many systematists and biogeographers have made their careers on predictions and modelling. We believe we can, for instance, predict divergence times based on molecular clocks. We attempt to predict which taxa and areas are ancestral based on models of evolution and geography. However none of these predictions are knowledge to the comparative biologist, as proponents of these models can never prove their predictions beyond a hypothesis, best guess or hunch. At best, they have tested, and to that extent warranted, theories. Warranted theories are far less reliable and certain than observations, and they hitchhike on data.
Call this "experimental envy" if you wish, but comparative biology is simply that - comparative. Knowledge for the comparative biologist lies in the ability to recognise organisms and their parts (as described above). If, for instance, a prediction proves to be true at some point in time, it was the comparative biologists' observation and knowledge of the organism, rather than a knowledge of a particular evolutionary process, that grounded that prediction. Theories and hypothesis are dependent on evidence (e.g., observation).
But knowledge of an organism is not enough. In their quest to predict and model, the contemporary comparative biologist is insisting a certain 'knowledge' of processes that extend beyond known and observable material phenomena. They claim to know what they cannot: that their hypotheses are true. Using their prior hypotheses, they ground their later ones on probabilities and likelihoods that are no better founded than the strength of the priors. Hypotheses build on hypotheses. This is inference, but it is not knowledge.
It appears that some comparative biologists appear to exhibit a certain form of non-religious and secular gnosticism - analogous to the gnosticism of atheists and theists described by Huxley when he coined the term "agnostic". That is, they claim to know more than what the evidence (i.e., data) can possibly claim. One example is ancestors. Having found the oldest known specimen of trilobite does not mean one has found the ancestor of all trilobites. What is known is that it is the oldest at the time of discovery - an older one may still exist. A trilobite's relations are inferred and always defeasible by new data. Data are not defeasible, however.
This phylogenetic agnosticism does not deny the existence of ancestors or centres of origin, only of our ability to recognise them with much certainty based on what we know (as opposed to what we merely think).
We recognise that a form of gnosticism has arisen in comparative biology since the 19th century due to the blurring of what we know for sure and what we believe we know. What we know is limited and restricted to what we can observe. What we believe to be happening, however, is not knowledge, but a best guess or informed opinion. Confusing it with actual knowledge creates a gnosticism that is already quite widespread in biology.
We appeal for warranted agnosticism, one that recognises the distinct difference between what we do know and what we believe we know. For instance, we may say that "I know this is a mammal" based on the diagnosis of mammals. We may also confidentially state that "I believe this to be the centre of origin for all palms" based our conviction of the truth of a theory of dispersal and speciation. For example we may be convinced that method x is better than say method y. On this basis we can determine which method is better. However, knowing which method is better does not guarantee that method will extend our knowledge of other unobservable processes.
What agnosticism in comparative biology is not, is banning, denigrating or rejecting certain hypotheses because they are not based on knowledge. Every comparative biologist has the right to express their convictions and opinions. They do not, however, have the right to confuse knowledge with a hypothesis. Doing so illicitly validates a hypothesis (i.e., a conjecture or best guess) as a discovery or known fact. A good comparative biologist is agnostic to all hypotheses and theories, until they are demonstrated to be true.
The highest happiness of man is to have probed what is knowable and quietly to revere what is unknowable (Goethe).
John S. Wilkins contributed a portion of this post. Please cite as Ebach, M.C., Wilkins, J.S. and Williams, D.M. (2011). Knowledge and Agnosticism in Comparative Biology. Systematics and; Biogeography Blog, http://urhomology.blogspot.com/2011/12/agnosticism-in-comparative-biology.html