Within the atheistic worldview, it is not possible to justify the validity of logic and truth.
Atheists commonly appeal to physical reality as their standard of logic and truth, which is equivalent to claiming that a vegetable, for example, can confirm valid logic because a vegetable is part of physical reality.
...Not only is this view ridiculous. It's also viciously circular, because it ultimately leads to the claim that "physical reality confirms physical reality" (i.e., we know that clouds produce rain because clouds produce rain). Obviously, rain clouds do not inject our minds with confirmation of the validity of our logical thought processes. Rather, we reason over such realities, and formulate conclusions solely within the mind.
But here's another perhaps even more powerful argument against the fallacious standard of physical reality:
Logic and truth are not limited only to the material world; logic and truth are also applied to immaterial/conceptual subject matter.
Consider the "transitive property of equality," for example:
This is purely a conceptual argument, independent of physical reality. It doesn't exist under a rock. You won't find it floating in space. Etc.
And yet, we know in our minds that the conclusion is logical and true - whether applied to physical reality or (other) concepts. Even if at some point in the past we became familiar with the concept of "equivalents" using physical reality as the basis, we know that physical reality never solved a logic puzzle or math equation, no matter how simple. No rational person would argue that a vegetable can deduce "A=C" based on the premises of the transitive property of equality!
Therefore, we can clearly demonstrate using this conceptual approach that logic and truth are confirmed in the mind, as opposed to being confirmed by...
...vegetables (physical reality).
Why is this important? It's important because it demonstrates that "MIND is the absolute standard" of logic and truth. And it follows from there that no human mind could serve as an absolute standard, because no human mind is perfect...
This in turn leads to the conclusion that a transcendent mind (i.e., the mind of God), must therefore be the absolute standard of logic and truth!
Jesus answered, "I am the way and the TRUTH and the life. No one comes to the Father except through me." - John 14:6
Jesus doesn't (only) state that His existence is true or that His words are true. He states that He *is* the truth... The absolute standard! This "Transitive Truth of Jesus" is passed to we who are more than flesh, created in the image and likeness of God.
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