This morning, because of some personal inner wrestling, I found myself seeking comfort from Philippians 4:8, which reads (ESV):
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things.
When you find your mind fixated on negatives, this passage can be a great help. It reminds us to fill our mind with those things which are positive. However, it is too easy to misunderstand this passage and think of it as a sort of positive confession or as an example of early pop-psychology. This would be an error. It is not saying to simply think happy thoughts. It is not telling us that claiming good things will make them a reality. While the latter parts of the passage can be misunderstood this way, the very first encouragement prevents it.
The passage begins by telling us to think about “whatever is true”. I found myself wondering how the author meant this word. Did he mean “true” as in the correspondence view of truth, meaning it is something that corresponds with reality? Is it possible that the apostle Paul was commanding us to think about what is true and mean that which is “reliable, unfailing and sure”? It is very important for us to understand exactly what Paul intended. Each definition includes different materials for us to fill our minds with. The latter group would be a much smaller group than the former correspondence definition.
If Paul is commanding us to think about those things that are sure and unchanging then we have a very small group included. However, if he intends us to understand “true” as everything that corresponds to reality, then we get a different feel for this part of the passage.
Paul is commanding us to look at what is factually true. To honestly look at what corresponds to reality. We are not called to imagine things as better than they are, but to honestly look at how they truly are. We are called to be people who accept and act upon the truth. One of the greatest causes of depression is the lies we tell ourselves. You can convince yourself that you are worse off than you actually are. You can be certain that the true condition of your life is false. You can build your actions upon lies that you have told yourself.
This actually informs our view of the rest of the passage. We are to think about those things which are truly honorable, truly just, truly pure, truly lovely, truly commendable, truly excellent, and truly praise-worthy.
 Analytical Lexicon of the Greek New Testament