Is the earth old or young? What difference does it make?
Suppose you walked outside and picked up a stone containing a fossil. If you had no preconceived ideas about how or when the rock was formed, or how the organism became fossilized, then how would you determine its age? Fossils do not come pre-labeled with their ages, nor with the day they were formed. The fossil exists in the present, and in order to infer an age from this present-day evidence, we must interpret the evidence. This requires that we come to the fossil with certain assumptions about the past in order to establish an age for the fossil.
If we believe that the Bible is accurate when it says that God flooded the whole earth in the days of Noah, then it would be natural to suggest that the fossil was formed by flood-borne sediment and is only a few thousand years old. If, on the other hand, we assume that the earth is billions of years old, and that the rock layers were deposited by successive periods of submersion and uplift over millions of years, then we may well conclude that the fossil is millions of years old.
Thus, it would be incorrect to say "The evidence speaks for itself." Rather, evidence must be interpreted by a set of assumptions, and the assumptions you start with can make a tremendous difference in the conclusions you draw from the evidence.
Often, people are not aware of their preconceived assumptions, and so they suppose they are being entirely neutral and objective when examining the evidence. In order to be as objective as possible, a person first needs to be aware that they have starting assumptions, and that these starting assumptions bias their interpretation of the evidence. They also need to be aware that a different set of assumptions could lead to very different conclusions. We need to realize that our starting assumptions are strongly-held beliefs, perhaps reinforced by teachers, parents, peers or media. We need to critically analyze these beliefs to see whether they are warranted, and we need to be aware that others may have different starting assumptions that also need to be analyzed and tested.
The various starting assumptions (presuppositions) we use to interpret the world around us will influence what we believe about nearly every subject—morality, truth, beauty, God, the afterlife, human worth—just to name a few. A set of presuppositions, together with the resulting way we understand the world around us is called a "worldview". Your worldview may lead you to be a Mother Teresa or an Adolph Hitler, both of whom lived their lives according to the way they understood the world to be.
I am not suggesting that truth itself is relative—it is not. The fossil
discussed earlier has an actual age, and it is not the actual age of the
fossil that depends on your presuppositions, but rather your interpretation
of the age of the fossil. In other words, the correctness of your conclusions
depends on the correctness of your starting assumptions.
Validating a Worldview.
How then do we determine if a set of starting assumptions, and the worldview they entail, are correct? In order to test a worldview for correctness, we should look for consistency. A false worldview will lead to contradictions, whereas a true worldview will be free from contradictions and will make sense of the world around us.
For example, those who hold to "relative morality" say that there are no moral absolutes, and that everyone should be free to do whatever they want as long as they don't impose their moral values on others. However, by saying "everyone should ... " they are asserting a moral absolute and seeking to impose it on others. True relative morality would say that "anything goes"—anyone can do anything they want to anyone they want, without restraint. However, this would lead to some people forcing their will on others, which is exactly what the moral relativists abhor. Moral relativists claim they do not believe in moral absolutes, yet they insist on at least one moral absolute: namely, that people are not permitted to assert their will over others. Where did they get this moral absolute? Why do they believe it to be more valid or binding than other moral absolutes? How do they justify it when their starting assumptions insist that there are no moral absolutes? In order to enforce this law, they must assert their will on others, thereby violating the very principle they claim to believe. These considerations prove that true moral relativism is impossible. It is a logical absurdity. Everyone believes in moral absolutes—even while attempting to deny them.
In contrast, the wrong way to test a worldview would be to use the assumptions
of a competing worldview to judge its conclusions. For example, it is invalid
for an atheist to criticize the Christian worldview by asserting that "miracles
are impossible". Miracles are impossible in the atheistic worldview, to
be sure; but this is simply because miracles, by definition, are the work
of a deity. However, the Christian worldview affirms the existence of a
God who is able to work miracles. If the atheist wishes to critique the
Christian's belief in miracles, he needs to show how miracles are inconsistent
with the Christian's presuppositions. This is called an "internal critique"—judging
a worldview on the basis of its own starting assumptions. We need
to step into our opponent's worldview in order to validly critique his
worldview. We need to show how his worldview is inconsistent with his
assumptions—regardless of whether it agrees with our own.
Validating a Scientific Theory.
A scientific theory is always based on a worldview, since the theory involves a particular way of thinking about the world. Just as we can test a worldview for logical consistency, there are also ways to test scientific theories. A valid scientific theory must be able to make specific predictions that can be tested.
For example, the theory of biological evolution claims that all plant and animal life evolved by gradual change over millions of years, and that the fossils provide a chronological record of this change. In this case, we would expect to see gradual change in the fossil record, with transitional fossils at virtually every stage of development. Yet, evolutionists have examined millions of fossils for over 150 years, and have repeatedly lamented the fact that the transitional fossils they expected to find are not there. In fact, they have found no undisputed transitional fossils connecting any of the major classes or phyla. This was admitted, for example by the renowned evolutionist, George Gaylord Simpson, in his book Tempo and Mode in Evolution. Steven Jay Gould, another prominent evolutionist, called this "the trade secret of paleontology".
In contrast to this, the Bible claims that God created distinct "kinds"
of animals, and designed them to procreate "after their kind" (Genesis
1:25; 6:20). While it is obvious that there is variability within specific
kinds—for example, there are many breeds of dogs, horses, cattle, ducks,
rabbits, etc.—it is also the case that we never observe real evidence
of transition between kinds. Dogs give birth only to dogs, horses beget
only horses, cattle produce only cattle, etc. There has never been any
observed evidence of a transition from one general kind to another, nor
of a common ancestor linking two or more kinds.
Observed evidence confirms the Biblical explanation, while refuting the
In summary, evidence has no voice—it does not "speak for itself", but must be interpreted. The criteria we use for interpreting evidence are certain "starting assumptions" or "presuppositions" that serve as the basis for our worldview. These presuppositions are, of necessity, merely beliefs and not facts deducible from prior facts or assumptions, for they are, after all, starting assumptions. In order to test a worldview, we look for inconsistencies or contradictions that would disprove the worldview. Any given worldview must be tested by its own starting assumptions, and not by those of a competing worldview.
When asking the question, "Is the earth old or young?" we need to realize
that we are dealing with entire worldviews, with all their presuppositions
and intertwining explanations. There is no point in attempting to argue
for a young earth in the absence of a global flood that explains the fossil
evidence. The question is ultimately much larger than simply "How old is
the earth?" The ultimate question is "Is the Bible authoritative on every
subject it addresses?" If the Bible cannot be trusted when it says that
God created the world in six days, then it cannot be trusted on other matters
either. But if the Bible is truly the authoritative Word of God, as it
claims to be, then it is equally authoritative when it says "in six
days God created the heaven and the earth" (Exodus 20:11) as when it
says "You shall not murder." (Exodus 20:13).
 "This regular absence of transitional forms is not confined to mammals, but is an almost universal phenomenon, as has long been noted by paleontologists. It is true of almost all orders of all classes of animals, both vertebrate and invertebrate. A fortiori, it is also true of the classes, and of the major animal phyla, and it is apparently also true of analogous categories of plants." G. G. Simpson, Tempo and Mode in Evolution (New York, Columbia University Press, 1944), p. 107.
 "The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils." Stephen Jay Gould, "Evolution's erratic pace", Natural History, vol. LXXXVI(5), May 1977, p. 14.
Genetic similarity is sometimes cited as proof of common ancestry. However,
this would be a proof of common ancestry only if there were no other way
to explain genetic similarity. A common Designer is an alternative explanation—one
who designed our food supply (plants and animals) to be biochemically compatible
with our human chemistry.