Cardinal Mercier's A Manual of Modern Scholastic Philosophy is a standard work, prepared at the Higher Institute of Philosophy, Louvain, mainly for the use of clerical students in Catholic seminaries. Though undoubtedly elementary, it contains a clear, simple, and methodological exposition of the principles and problems of every department of philosophy, and its appeal is not to any particular class, but broadly human and universal.
Volume I includes a general introduction to philosophy and sections on cosmology, psychology, criteriology, and metaphysics or ontology.
Mercier’s manual is a great overview for anyone with an intermediate level understanding of thomism, like myself. I describe it as an “intermediate” text, but this is only in comparison to the thomistic tradition. Even an intermediate thomist text is more sophisticated than 99% of contemporary philosophy. It displays all of the characteristic virtues and shortcomings of that era of thomism. On the one hand, it is clear, well-organized, and thorough. Mercier’s thought is always precise and takes full advantage of the developments of the thomist tradition. On the other hand, sometimes Mercier is more Suarezian or Kantian than I would like (though his Kantian tendencies are sometimes a positive).