Perhaps the best defense of the utility of philosophy for Christian ministry is found in Moreland and Craig's Philosophical Foundations for a Christian Worldview (16-19). The following is my summary of six benefits:
Apologetics – when an objection is made against Christianity it is almost always a philosophical objection or involves a philosophical assumption. Just consider the following objections: (i) there is no evidence for the existence of God (ii) miracles are impossible (iii) the presence of evil in the world entails that God does not exist (iv) How do we know that the bible is true? (v) How can Christianity be the only way to God? (vi) That might be true for you but not for me (vii) How do you know that Jesus was raised from the dead? All of these objections require philosophical replies.
Polemics – the church is called upon to criticize and refute false views. One important way to refute erroneous views is by philosophical argument. Refuting people in political debate requires that we have a philosophical acumen in regards to ethics, views of human nature etc. Philosophical refutations are (a) more powerful, yielding necessary truths (b) accessible to most people if we avoid technical language.
Expression of Image of God – If God has made us in his image and at least in part this entails that we think like him, then we should be trained to use our mental faculties to the greatest measure. Thinking rationally, ethically, and deeply about the most fundamental questions of truth, reality, logic, language, knowledge, and values is to use one’s mental faculties at the highest level, getting the most out of what God has given us (parable of the talents).
Plato thought philosophers should rule others; we think they should serve others.
As a ‘handmaid’ to theology – Whereas Plato thought philosophers should be kings, as Christians we think of them as servants. Our primary master is theology, the ‘queen of the sciences’. We serve by (a) clarifying concepts and statements. The most annoying thing we do might be the most helpful – we keep asking ‘what do you mean by…?’ (b) “extending biblical teaching to issues on which the Bible is not clear/explicit." Bio-ethics is a good example of philosophical work with direct application but no clear biblical teaching, and (c) enhancing the study of the Bible through aiding interpretation skills. Philosophical reflection on the logic of arguments, definitions of terms, assumptions of premises, coherence of statements, and framework of issues are beneficial for the interpretation of scripture (d) even if you do not want to do much philosophical work but do wish to understand theological work, it is likely that those theological works are done by people with a great deal of philosophical acumen. Having a minimal understanding of philosophy will greatly aid you in your theological studies (you better understand Augustine if you understand Plato/Plotinus; you better understand Aquinas if you understand Aristotle; you better understand Barth if you understand Kant; you better understand progressive postmodern theology if you grasp the central tenets of postmodern philosophy)
Enhance the confidence of the Christian in the world – (a) “Historically, philosophy has been the main discipline that has aided the church in its intellectual relationship with unbelievers. Because of the very nature of philosophy itself—its areas of study and their importance for answering ultimate questions, the questions it asks and answers, its closeness to theology—the potential of this discipline for enhancing the self-respect of the believing community is enormous.” (M and C, 18). This is as true now as it was in Justin Martyr, Origen, and even in Tertullian’s time! (b) Philosophical skills are very demanding! So, developing philosophical skills will give us more power to contribute to our own Christian community and more confidence in what we believe.
Essential for integration – Not all our beliefs are in propositions expressed in the Bible. Integration is the act of blending, combining all our beliefs from all the disciplines into a coherent whole. Human beings do not do well if they are fragmented, if their beliefs in one area conflict with their beliefs in other areas. Philosophers are uniquely equipped to integrate disciplines because (i) philosophers are already involved in every discipline as a second-order discipline, and (ii) philosophers are model-builders, they are always attempting to integrate systems of thought into a coherent whole.