A planner driven by a causal theory and based on hypothetical reasoning is constructed and discussed. The task is approached from the fundamentals of time and event logics, and causality, resulting in a planner suitable for modeling a wide variety of realistic problem domains, and capable of reasoning in an intuitive manner about dynamic domains. The underlying causal theory drives the planning process directly and, in conjunction with the uniform representation of time and causal facts, allows elegant solutions to planning problems. A new type of planning problem, the indirect goal problem, is identified and solved It is also shown that previous planners cannot solve this type of problem. The frame problem is discussed in detail, and given a computational definition, suitable for allowing objective comparison between different approaches. The hypothetical reasoning approach is shown to allow an elegant solution to the frame problem appropriate for planning systems. / Master of Science