This book is designed to explain the technical ideas that are taken for granted in much contemporary philosophical writing. Notions like denumerability modal scope distinction Bayesian conditionalization & logical completeness are usually only elucidated deep within difficult specialist texts. By offering simple explanations that by-pass much irrelevant & boring detail Philosophical Devices is able to cover a wealth of material that is normally only available to specialists. The book contains four sections each of three chapters. The first section is about sets & numbers starting with the membership relation & ending with the generalized continuum hypothesis. The second is about analyticity a prioricity & necessity. The third is about probability outlining the difference between objective & subjective probability & exploring aspects of conditionalization & correlation. The fourth deals with metalogic focusing on the contrast between syntax & semantics & finishing with a sketch of Godels theorem. Philosophical Devices will be useful for university students who have got past the foothills of philosophy & are starting to read more widely but it does not assume any prior expertise. All the issues discussed are intrinsically interesting & often downright fascinating. It can be read with pleasure & profit by anybody who is curious about the technical infrastructure of contemporary philosophy.