For my purposes in this particular post, when I use the term evolution, I am referring to natural selection as proposed by Charles Darwin in On the Origin of Species i.e. Darwinism.
Now, as someone who believes that "God created the heavens and earth," I sometimes find myself being labeled as "religiously bias." Many are quick to assert that those who believe in a designer are unable to view scientific evidence (or any for that matter) objectively because of their religious convictions. However, after pondering the question for quite sometime, it is my conviction that the theist actually finds himself in the more objective position than that of the materialist.
Science, as defined by the current scientific community, basically states that science is the search for natural causes only.
Consider the following words from one of Carl Sagan's friends, Harvard's Richard Lewontin:
Our willingness to accept scientific claims that are against common sense is key to an understanding of the real struggle between science and the supernatural. We take the side of science in spite of the patent absurdity of some of its constructs, in spite of its failures to fulfill many of its extravagant promises of health and life, in spite of the tolerance of the scientific community for unsubstantiated just-so stories, because we have a prior commitment to materialism. In is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter intuitive, no matter how mystifying to the uninitiated. Moreover the materialism is absolute for we cannot allow a divine foot in the door. 
In other words, the game is rigged before it's played!
With that in mind, it's important to remember that science is supposed be, or at the very least, should be, the search for that which is true. However, when one claims that "science is the search for natural causes only," he or she, knowingly or unknowingly, is guilty of allowing there philosophical bias to enter into their scientific conclusions. To be specific, materialistic science is based upon the philosophy (or some may even say religion) of materialism- the belief that the material is all there is. This idea is of course problematic because we have good reasons to believe that immaterial things do exist.
Dr. William Lane Craig offers some examples:
1. mathematics and logic
2. metaphysical truths (such as, there are minds that exist other than my own),
3. ethical judgements (you can't prove by science that the Nazis were evil, because morality is not subject to the scientific method),
4. aesthetic judgements (the beautiful, like the good, cannot be scientifically proven), and, ironically
5. science itself (the belief that the scientific method discovers truth can't be proven by the scientific method itself) 
If one doubts this, I'll simply point out that the very thought that, "only nature (or the material) exists," is itself immaterial! It is an idea with no weight, mass, etc. If one were to crack a materialists head open (which I don't recommend doing!), you would not find the idea "only the material exists" inside their head.
Contrast this with the theistic worldview. As a theist, I am free to follow the evidence wherever it leads because my philosophical convictions don't box me in. Admittedly, one should always consider natural explanations first; however, if detectable design is present, one should be at liberty to conclude that a designer is the best explanation of the phenomenon being observed. It's important to highlight that those who preach materialistic science do observe what they would call the "appearance" of design-
Richard Dawkins asserts:
"Biology is the study of complicated things that give the appearance of having been designed for a purpose." 
Further, Francis Crick, the co-discoverer of DNA, admits:
"...biologists must constantly keep in mind that what they see was not designed, but rather evolved." 
So, it isn't that the design is unobserved, but when the observable science challenges the philosophical bias (in this case, materialism), the observable science takes a back seat to the philosophy- materialism.
Moreover, as a theist, I am free to accept, or reject, evolution based solely on it's scientific merits. Hypothetically, if I were to conclude that evolution, on a macro-evolutionary level (change at or above the level of species) , were true, this would do nothing to undermine my worldview. As a Christian, I would certainly have to reevaluate some of my views; however, a Creator would still be the best explanation of 1) the origin of the universe 2) the fine-tuning of the universe 3) objective moral values and duties 4) Jesus' resurrection from the dead 5) the information found in DNA 6) and human consciousness.
But what about the materialist (or naturalist) who says that "nature is all there is?" He or she, because of their philosophical bias, cannot even consider design. They have already decided a priori, that a naturalistic explanation must explain everything, no matter what. They cannot "let a divine foot in the door." This is simply assuming what you are trying to prove.
Ironically, it is not Intelligent Design or Theism that is a "science stopper," as many of it's opponents would have us believe, but it is science based upon materialism that keeps the scientist from being able to follow the evidence.
Further, it seems hypocritical to me when materialists object to ID because it has "theistic implications," when, if they were honest, materialism clearly has atheistic implications.
It is for these reasons that I believe the theist finds himself in a more objective position than the materialist.
Courage and Godspeed,
1. Richard Lewontin, "Billions and Billions of Demons," The New York Review of Books, January 9, 1997, 31.
2. A debate between William Lane Craig and Peter Atkins; the debate can be read here: http://www.leaderu.com/offices/billcraig/docs/craig-atkins.html
3. Richard Dawkins, The Blind Watchmaker, 1.
4. Francis Crick, What Mad Pursuit (1990), p. 138.
5. John Wilkins, "Macroevolution: Its Definition, Philosophy and History," http://www.talkorigins.org/faqs/macroevolution.html#what.