Although experimental evidence for retrocausation exists, there are clearly subtleties to the phenomenon. The bilking paradox, in which one intervenes to eliminate a subsequent cause after a preceding effect has occurred, appears on the surface to show that retrocausation is logically impossible. In a previous paper, the second law of thermodynamics was invoked to show that the entropy in each process of a psi interaction (presentience, telepathy, remote perception, and psychokinesis) cannot decrease, prohibiting psi processes in which signals condense from background fluctuations. Here it is shown, perhaps contrary to one’s intuition, that reversible processes cannot be influenced through retrocausation, but irreversible processes can. The increase in thermodynamic entropy in irreversible processes — which are generally described by Newtonian mechanics but not Lagrangian dynamics and Hamilton’s Principle — is required for causation. Thermodynamically reversible processes cannot be causal and hence also cannot be retrocausal. The role of entropy in psi interactions is extended by using the bilking paradox to consider information transmission in retroactive psychokinesis (PK). PK efficiency, ηPK, is defined. A prediction of the analysis is that ηPK ⩽ H/H0, where H is the information uncertainty or entropy in the retro‐PK agent’s knowledge of the event that is to be influenced retrocausally. The information entropy can provide the necessary ingredient for non‐reversibility, and hence retrocausation. Noise and bandwidth limitations in the communication to the agent of the outcome of the event increase the maximum PK efficiency. Avoidance of the bilking paradox does not bar a subject from using the premonition of an event to prevent it from occurring. The necessity for large information entropy, which is the expected value of the surprisal, is likely to be essential for any successful PK process, not just retro‐PK processes. Hence uncertainty in the communication process appears to be a necessary component of retrocausation in particular, and of PK in general.
Although experimental evidence for retrocausation exists, there are clearly subtleties to the phenomenon. The bilking paradox, in which one intervenes to eliminate a subsequent cause after a preceding effect has occurred, appears on the surface to show that retrocausation is logically impossible. In a previous paper, the second law of thermodynamics was invoked to show that the entropy in each process of a psi interaction (presentience, telepathy, remote perception, and psychokinesis) cannot decrease, prohibiting psi processes in which signals condense from background fluctuations. Here it is shown, perhaps contrary to one’s intuition, that reversible processes cannot be influenced through retrocausation, but irreversible processes can. The increase in thermodynamic entropy in irreversible processes — which are generally described by Newtonian mechanics but not Lagrangian dynamics and Hamilton’s Principle — is required for causation. Thermodynamically reversible processes cannot be causal and hence also cannot be retrocausal. The role of entropy in psi interactions is extended by using the bilking paradox to consider information transmission in retroactive psychokinesis (PK). PK efficiency, ηPK, is defined. A prediction of the analysis is that ηPK ⩽ H/H0, where H is the information uncertainty or entropy in the retro‐PK agent’s knowledge of the event that is to be influenced retrocausally. The information entropy can provide the necessary ingredient for non‐reversibility, and hence retrocausation. Noise and bandwidth limitations in the communication to the agent of the outcome of the event increase the maximum PK efficiency. Avoidance of the bilking paradox does not bar a subject from using the premonition of an event to prevent it from occurring. The necessity for large information entropy, which is the expected value of the surprisal, is likely to be essential for any successful PK process, not just retro‐PK processes. Hence uncertainty in the communication process appears to be a necessary component of retrocausation in particular, and of PK in general.
Retrocausation seems to admit of time paradoxes in which events prevent themselves from occurring and thereby create a physical instance of the liar's paradox, an event which occurs iff it does not occur. The specific version in which a retrocausal event is used to trigger an intervention which prevents its own future cause is called the bilking paradox (the event is bilked of its cause).The analysis of Echeverria, Klinkhammer, and Thorne (EKT) suggests time paradoxes cannot arise even in the presence of retrocausation. Any self‐contradictory event sequence will be replaced in reality by a closely related but noncontradictory sequence. The EKT analysis implies that attempts to create bilking must instead produce logically consistent sequences wherein the bilked event arises from alternative causes.Bilking a retrocausal information channel of limited reliability usually results only in failures of signaling. An exception applies when the bilking is conducted in response only to some of the signal values that can be carried on the channel. Theoretical analysis based on EKT predicts that, since some of the channel outcomes are not bilked, the channel is capable of transmitting data with its normal reliability, and the paradox‐avoidance effects will instead suppress the outcomes that would lead to forbidden (bilked) transmissions.A recent parapsychological experiment by Bem displays a retrocausal information channel of sufficient reliability to test this theoretical model of physical reality's response to retrocausal effects. A modified version with partial bilking would provide a direct test of the generality of the EKT mechanism.
Evidence for retrocausation in the field of psychophysical phenomena is to date questionable. Associated successful theoretical formulations would have to make accurate predictions and the purported evidence would have to be independently replicated. It is shown here that purported evidence for retrocausation within the field of psychophysical phenomena, such as the hypothesis of micro‐PK —that the statistical distributions of random processes are mean shifted by thought alone— can find more satisfactory descriptions. Those do not necessarily invoke transfer of information backward in time, while they provide mathematically structured formulations and allow for clear predictions. They refer to a two‐state Markovian process characterized by equal self‐transition probabilities, p=q>50%. This Markovian behavior introduces persistence and clustering of like binary states leading to a broadened scatter of statistical averages of individual micro‐PK tests about their theoretically expected mean, namely 50%, corresponding to that of an unbiased process. The origin of this broadening mechanism is currently unclear. It is, therefore, argued here that an established theory of mind‐matter interaction should precede the investigation of the validity of retrocausation within psychophysical phenomena. Thus the correct theory can be decided among alternatives.
The possibility of retrocausation has been considered to explain the occurrence of anomalous phenomena in which the ostensible effects are preceded by their causes. A scrutiny of both experimental methodology and the experimental data is called for. A review of experimental data reveals the existence of such effects to be a serious possibility. The experimental methodology entails some conceptual difficulties, these depending on the underlying assumptions about the effects. A major point is an ambiguity between anomalous acquisition of information and retrocausation in exerted influences.A unifying theory has been proposed, based upon the fundamental randomness of quantum mechanics. Quantum mechanical randomness may be regarded as a tenacious phenomenon, that apparently is only resolved by the human observer of the random variable in question. This has led to the “observational theory” of anomalous phenomena, which is based upon the assumption that the preference of a motivated observer is able to interact with the extant indefinite random variable that is being observed. This observational theory has led to a novel prediction, which has been corroborated in experiments. Moreover, different classes of anomalous phenomena can be explained by the same basic mechanism. This foregoes retroactive causation, but, instead, requires that macroscopic physical variables remain in a state of indefinite reality and thus remain influenceable by mental efforts until these are observed. More work is needed to discover the relevant psychological and neurophysiological variables involved in effective motivated observation. Besides these practicalities, the fundamentals still have some interesting loose ends.
This paper presents a conceptual and analytical investigation into the limits of temporal access through the combined perspectives of causality, relativity, quantum mechanics, thermodynamics, and information theory. The work introduces the concept of the “Temporal Causality Barrier,” a selective and logically grounded framework that distinguishes between passive temporal observation and active temporal intervention. The paper argues that passive observation of the past is both physically permissible and continuously occurring through ordinary causal processes such as light propagation, memory, historical records, and astronomical observation. In contrast, active intervention into the past including backward information transfer, causal alteration of previous events, and closed causal loops is shown to generate logical contradictions and violations of causal consistency. The analysis critically examines major theoretical approaches related to time travel and retrocausality, including closed timelike curves, Novikov’s self-consistency principle, Deutsch’s quantum closed timelike curve model, and the two-state vector formalism in quantum mechanics. The paper argues that while some interpretations may mathematically describe retrocausal correlations, none currently provide an operational mechanism for backward information transmission without encountering paradoxes or information-theoretic inconsistencies. The framework further connects the causal structure of spacetime with the thermodynamic arrow of time, emphasizing the role of entropy, light cone geometry, and information propagation in preserving temporal coherence. The work also explores broader philosophical implications concerning the nature of time, consciousness, causality, and agency within a causally structured universe. Rather than proposing a new physical force or replacing existing theories, this paper provides a logically structured analysis of why temporal observation is compatible with known physics while active temporal intervention remains fundamentally constrained by both physical law and logical consistency.
The principle of cause and effect is deeply rooted in human experience, so much so that it is routinely and tacitly assumed throughout science, even by scientists working in areas where time symmetry is theoretically ingrained, as it is in both classical and quantum physics. Experiments are said to cause their results, not the other way around. In this informal paper, we argue that this assumption should be replaced with a more general notion of mutual influence — bi‐directional relations or constraints on joint values of two or more variables. From an analysis based on quantum entropy, it is proposed that quantum measurement is a unitary three‐interaction, with no collapse, no fundamental randomness, and no barrier to backward influence.Experimental results suggesting retrocausality are seen frequently in well‐controlled laboratory experiments in parapsychology and elsewhere, especially where a random element is included. Certain common characteristics of these experiments give the appearance of contradicting well‐established physical laws, thus providing an opportunity for deeper understanding and important clues that must be addressed by any explanatory theory. We discuss how retrocausal effects and other anomalous phenomena can be explained without major injury to existing physical theory. A modified quantum formalism can give new insights into the nature of quantum measurement, randomness, entanglement, causality, and time.
PK experiments with prerecorded targets (Schmidt, 1976) are interesting because they suggest a variety of new test arrangements to study the basic PK mechanism. In addition, they permit the inclusion of independent observers who, with little time investment, can obtain first-hand evidence of any anomalous effects that may occur. Four such experiments with different independent observers, different subject populations, and minor variations have been performed previously (Schmidt & Braud, 1993; Schmidt, Morris, & Hardin, 1990; Schmidt, Morris, & Rudolph, 1986; Schmidt & Schlitz, 1988) with the first author as main experimenter and the other one or two authors acting as independent observers. The results of PK experiments with prerecorded random events appear most interesting and most puzzling because the subject's mental effort is made long after the random events to be affected have occurred. One tentative viewpoint (Schmidt, 1978; Walker, 1979) is that the subject's mental effort could act backward to the time when the random events were generated and recorded. This would imply a noncausal mechanism in the sense that the effect (the biasing of the random events) occurs before the cause (the mental effort). It might be this element of noncausality that makes psychic phenomena so intuitively implausible and at odds with the known principles of physics. Another viewpoint (Schmidt, 1982) is based on the quantum theoretical notion that there is no if there is no observer. Thus, the decisions of the random generator might become reality only when the subject observes the outcome during the test session. The subject's effort would not have to act into the past because the decision on the outcome would not yet be made until the subject received feedback during the PK test session. In this case, a preobservation of the recorded events should inhibit the subject's success, because the preobservation would make the random decisions real so that the subject's subsequent mental effort would come too late. For this reason it seemed particularly interesting to conduct an experiment in which half of the prerecorded random events had been preinspected so that one could compare the possible PK effects on the preobserved and not-observed events. One previous study (Schmidt, 1985) has indicated an inhibition of the PK effect by preobservation. In view of the central role of the question, however, further studies of the preobservation effect seem most important. In this and the four previous studies, the question of highest priority was whether a PK effect could be demonstrated under tightly controlled conditions. Because preobservation might inhibit the PK effect, we decided in advance to base the possible evidence for the existence of PK only on the results from the not-preobserved events. Although the independent observer was somewhat skeptical about the existence of PK, he was very interested in a possible preobservation effect because of its possible implications for quantum theory. Our subject pool consisted primarily of martial arts students as a matter of practical convenience. This population was relatively easily accessible and one that the experimenter had not yet explored. No attempt was made, however, to compare martial arts training and skill with PK performance systematically. METHOD The study was structured into 20 units such that a unit could be considered as a mini-experiment. Each unit was subdivided into 100 blocks of binary data. The sequence of binary data in each block determined two partial results, an even result and an odd result, arising from the even- or odd-numbered bits in the sequence. The partial results were defined so that by inverting the bits in the sequence (interchanging 1s and 0s) the signs of the partial results were inverted. In following the procedure for each unit, the experimenter used a true random generator to record the random bit-sequences for the 100 blocks on floppy disk. …