The title "Introduction to Philosophy" is not only banal but misleading and, above all, does not do justice to the formidable work that Maritain does in this book. The book is an overview of Aristotelian and (neo)Thomistic philosophy and goes deeper into its intricacies than any "introduction to philosophy" I have seen.
The first part of the book makes the case that Aristotle was the greatest philosopher of all time. The inanity of such a claim is only apparent, as Maritain's plea demonstrates. It certainly made me reassess my dismissal of much of Aristotelian and Thomistic philosophy, which I admit I have been guilty of on too flimsy grounds.
The second part looks into the nitty-gritty of Aristotelian and (neo)Thomistic philosophy. It seems trite but, at closer inspection, it appears trite because it makes sense, which is exactly what Aristotelian philosophy prides itself on. Maritain's exposition revolves around one term: intellect and its cognates, such as intelligible, intelligibility. Maritain is not ashamed to admit that intellect is in line with what we call the common sense. Regrettably, common sense is a much maligned concept in contemporary philosophy because of its supposedly unavoidable ideological underpinnings. Maritain made me reassess the bad press which has been heaped on "common sense" in our time.
Another much maligned concept Maritain feasts on is metaphysics, which is in practice natural theology, that part of philosophy that points us to God without the help of divine revelation. Metaphysics is a servant of revealed or supernatural theology in the sense that nothing a theologian says can contradict metaphysics (or other branches of philosophy, such as logic, ethics etc. for that matter).
Maritain is not wholly devoid of pedantry (hence that one missing star in my rating) in his explanation of "essence" as opposed to "existence" and "substance" as opposed to "accidents" etc. Again, the problem seems to be that the distinctions sound as so much hair-splitting. Do we not already know this, the reader may ask himself. However, this is the type of collateral damage that Maritain gladly accepts because the force of Aristotelian philosophy is that it makes sense and its concepts are...intelligible. No matter how many foreign-sounding concepts Maritain parades, there is nothing that the reader does not already know somehow.
Even if Aristotelian philosophy does not have the reputation of being "cool" at the moment, his philosophy does have the power to demolish more recent philosophies which, by implication, do NOT make sense! Maritain explains that the attraction of such philosophies is that they have been developed by some supposedly exceptional individual regardless of whether they make sense or not. And they do not. That it not their strength but their weakness and, ironically, their weaknesses redound to bolstering the case of Aristotle, as Maritain demonstrates. Successfully, I think.