Reasoning about causal relationships is central to the human experience. This evokes a natural question in our pursuit of human-like artificial intelligence: how might we imbue intelligent systems with similar causal reasoning capabilities? Better yet, how might we imbue intelligent systems with the ability to \textit{learn} cause and effect relationships from observation and experimentation? Unfortunately, reasoning about cause and effect requires more than just data: it also requires partial knowledge about data generating mechanisms. Given this need, our task then as computational scientists is to design data structures for representing partial causal knowledge, and algorithms for updating that knowledge in light of observations and experiments. In this dissertation, I explore the \textit{Bayesian structural} approach to causal inference in which probability distributions over structural causal models are one such data structure, and probabilistic inference in \textit{multi-world} transformations of those models as the corresponding algorithmic task. Specifically, I demonstrate that this approach has two distinct advantages over the dominant computational paradigm of causal graphical models: (i) it expands the breadth of compatible assumptions; and (ii) it seamlessly integrates with modern Bayesian modeling and inference technologies to facilitate quantification of uncertainty about causal structure and the effects of interventions. Specifically, doing so allows the emerging and powerful technology of probabilistic programming to be brought to bear on a large and diverse set of causal inference problems.
In Chapter 3, I demonstrate how priors over structural causal models induce joint distributions over observed and latent counterfactual random variables, and I demonstrate how the resulting posterior distributions over causal effects capture common motifs in causal inference. In particular I show how various assumptions about latent confounding influence our ability to estimate causal effects from data. In addition, I provide examples of common observational and quasi-experimental designs expressed as probabilistic programs. In Chapter 4, I present an advanced application of the Bayesian structural approach for modeling hierarchical relational dependencies with latent confounders, and how to combine such assumptions with flexible Gaussian process models. In Chapter 5, I present a prototype software implementation for causal inference using probabilistic programming, accommodating a broad class of multi-source observational and experimental data. Finally, in Chapter 6, I present Simulation-Based Identifiability, a gradient-based optimization method for determining if any differentiable and bounded prior over structural causal models converges to a unique causal conclusion asymptotically.
Advisor: David Jensen