William Lane Craig On Guard: What It Actually Is and How to Use It
On Guard is a digital companion resource tied to William Lane Craig's work in philosophical apologetics. It's designed for people who want to study the arguments Craig lays out in his book On Guard: Thinking Faith Through the Backdoor. The resource walks through fifteen foundational topics in natural theology and philosophy of religion, giving you structured readings, video lectures, and discussion questions. It's not a standalone system. You need to already have some interest in these topics and be willing to put in reading time. The resource is hosted through Crossway and the ReasonableFaith.org ecosystem. You can access it at reasonablefaith.org/on-guard. There's also a mobile companion available through the Reasonable Faith app, which syncs your progress across devices. Some content requires a Crossway account, which is free to create. If you run into issues downloading or accessing material, clearing your browser cache usually resolves it. I had a problem where the video lectures wouldn't buffer past the first minute on Firefox. Switching to Chrome fixed it immediately. The issue seemed specific to that browser version. The structure is modular. Each of the fifteen topics has its own section. Inside each section you'll find a reading assignment, a lecture video from Craig or a guest speaker, a quiz, and optional discussion questions. The whole thing is designed to take roughly three to four weeks if you're moving through it at a moderate pace. That means about two topics per week. If you go faster, you'll miss nuance. If you go slower, the material stays fresh in your head better. I recommend the slower approach unless you're pressed for time.
The quizzes are multiple choice and self-graded. They check whether you actually read the material or just scrolled through it. The answers aren't always obvious. You'll need to re-read sections if you get questions wrong. That's by design. The program doesn't let you skip ahead until you pass the quiz for the current topic. This is both a feature and a frustration. When I was working through the cosmological argument module, I failed the quiz twice because I skimmed rather than studied. The third attempt required me to slow down and actually engage with the material. That's when it clicked.
Common Problems and What They Mean
The biggest issue people run into is that this resource assumes a baseline familiarity with basic logic and philosophy terminology. If you've never encountered the difference between a sound argument and a valid one, or if modal logic is completely new to you, you'll struggle. The program doesn't teach these prerequisites. You need to do supplementary reading on your own. I found myself going to Stanford Encyclopedia of Philosophy entries mid-module to understand terms like modality and possible worlds semantics. That's not an official part of On Guard. It's something you pick up along the way. Another practical problem is the pacing. The content is dense. A single video lecture can run forty-five minutes to an hour. The reading assignments are typically five to ten pages per topic. If you're doing this alone without a study group or accountability partner, motivation drops fast. I worked through topics three and four back to back and burned out by topic five. Splitting the schedule with rest days between topics made a noticeable difference in retention. There's also the question of what happens after you finish. The program doesn't automatically feed you into another course. You'll need to seek out follow-up material on your own. Craig's Reasonable Faith website has additional resources, and his book More Than a Carpenter is a logical next step. Some people move on to his academic papers, but those require a different level of engagement than the On Guard content. I'd suggest having your next destination mapped out before you start, otherwise you'll hit a wall when the twelve-week journey ends.
Get the Full Details
Who Should Use This
This works well for someone who wants a structured introduction to Christian apologetics and is willing to work through difficult material. It's not for casual browsing. The format demands participation. If you're looking for a quick overview or entertainment value, you'll be disappointed. The resource is also less useful if you already have a philosophy background. Advanced students will find the treatment too surface level for most topics. The sweet spot is someone with intellectual curiosity but limited formal training in philosophy or theology.
Bottom Line
The William Lane Craig On Guard resource is a solid entry point into philosophical apologetics. It covers the cosmological argument, the moral argument, the resurrection, and several other foundational topics. It won't make you an expert. It won't convert anyone on its own. But if you're serious about understanding these arguments and working through them systematically, it's one of the more accessible structured programs available. Just plan for the learning curve and have backup materials ready for when the program's scope runs thin.
