The reason is that we restrict our "explanations" to those starting from a ground atom which actually "causes" something, and Step **does not appear on** the left side of a *causal atom*. Notice however that, if Step **is established, then** so is Evolution from O1, thus, from E**4 we indeed get some "explanation" in**
which the left-hand side is established while the right-hand side is **Alarm**.

It must be noticed that here are cases (particularly when making abduction from a set of atoms) where it is convenient to derive also "explanations" starting from atoms such as Step **here. This addition is immediate in our formalism.**

## 5 Conclusion

We have provided a logical framework allowing predictive and abductive reasoning from *causal* **information. Indeed, the formalism allows to express causal**
information in a direct way. Then, we deduce so-called *explanation atoms* **which** capture what might explain what, in view of the given information. We have resorted to *ontological* **information, which is key in generating sensible explanations from causal statements.**
The user provides taxonomic information as a list of *ontological atoms* a →IS−A
b intended to mean that object a "is a" b**. The basic ground atoms, denoted** α, β, are then built with predicates, such as P(a, b**). The user provides causal**
information as causal atoms α causes β **(which can occur in more complex**
formulas). This makes formalization fairly short and natural. The ontology is used in various patterns of inference for explanations. Such information is easy to express, or to obtain in practice, due to existing ontologies and ontological languages. If we were in a purely propositional setting, the user should write Own small car →IS−A Own car, Own big car →IS−A Own car**, and also** Heard small car →IS−A Heard car **and so on.**
This would be cumbersome. In contrast, our setting is "essentially propositional" for what concerns the causal atoms, in that it is as if Own(small car)
were a propositional symbol Own small car, while, for what concerns the ontology, we really use the fact that Heard and Own **are predicates.**
The notion of predicates "essentially existential" or "universal" allows to keep a "datalog" formalism, very closed to a propositional one, without the need for explicit quantifiers ∀ (for all) or ∃ *(there exists)*.

The present proposal is a compromise between simplicity, as well as clarity, when it comes to describing a situation, and efficiency and pertinence **of the** results provided by the formalism.

Our work differs from other approaches in the literature in that it strictly separates causality, ontology and explanations. The main advantages are that information is more properly expressed and that our approach is compatible with various accounts of these notions, most notably causality. In **particular,**