Albert has published four books—
Quantum Mechanics and Experience (1992),
Time and Chance (2000),
After Physics (2015), and
A Guess at the Riddle (2023)—as well as numerous articles on
interpretations of quantum mechanics, the
direction of time, and other topics. His writing has been both praised and criticized for its informal, conversational style. His first two books are considered influential in the development of the contemporary literature on philosophy of physics.
Interpretations of quantum mechanics Albert's first book,
Quantum Mechanics and Experience, is regarded to have set a key research agenda in the philosophy of quantum mechanics: that of finding an interpretation of quantum mechanics that is
realist in the traditional philosophical sense. This program is in opposition to the
Copenhagen interpretation, most popular among working physicists, which had been criticized since its formulation as failing to give an account of observer-independent reality. In Albert's book, he explicates the
measurement problem and discusses three interpretations of quantum mechanics which aim to resolve this problem within the context of scientific realism:
Ghirardi–Rimini–Weber theory,
De Broglie–Bohm theory, and the
many-worlds interpretation. This "three-way debate" has framed much of the discourse on foundations of quantum mechanics in the decades since. In this book and his subsequent work, Albert has argued that the Everett (many-worlds) interpretation is incoherent or incomplete, failing to adequately account for
probabilities and the
Born rule. He has also argued for wave function realism, the view that the quantum
wave function is a concrete physical object, while the "geometrical appearances" of three-dimensional space are produced by the dynamics of the wave function. This contrasts with the "primitive ontology" view (promoted by Valia Allori and others) that objects in space and time are fundamental.
Past hypothesis Albert's second book,
Time and Chance, develops an approach to the foundations of statistical mechanics which aims to explain the time-asymmetries present in the macroscopic world (such as the asymmetry of
causality, the existence of records of the past, and the
second law of thermodynamics) in light of the observation that the microscropic dynamical laws are time-symmetric. Albert proposes that the fundamental laws of nature must include not only (1) these dynamical laws, but also (2) a
past hypothesis and (3) a statistical postulate. The past hypothesis is a claim that the universe was in a very
low-entropy state at some time in the distant past, and the statistical postulate is a probability distribution which specifies that a system in a given
thermodynamic macrostate is equally likely to be in each microstate compatible with that macrostate. He argues that these two additional postulates are sufficient to recover all the emergent time-asymmetries, including (for instance) the prediction that ice will melt in a warm room. While the notion a low-entropy state in the distant past has been discussed since the early days of
thermodynamics, Albert is credited with coining the term "past hypothesis" and identifying that classical mechanics cannot be understood as a complete, empirically adequate theory (even in classical contexts—i.e. disregarding relativistic and quantum-mechanical concerns) in the absence of a past hypothesis and statistical postulate. Subsequent work by Albert and his frequent collaborator
Barry Loewer has further developed the account from
Time and Chance into a comprehensive theory of the origin of physical probabilities, the relationship between fundamental physics and the
special sciences, and a physicalist explanation of
counterfactuals and
causality. This picture has come to be called the Mentaculus, after a line from the
Coen brothers film
A Serious Man referring to "the probability map of the universe". Albert has more recently argued that probability is indispensable in scientific explanations, and that standard mechanical predictions such as the orbits of the planets cannot be reliably reproduced in the absence of a statistical postulate. Albert and Loewer's account has generated much debate, and a collection of essays written in response to
Time and Chance and the Mentaculus picture was published in 2023. ==Public philosophy==