In this paper, I address Husserl’s theory of intentionality focusing on the problems of attention. I claim that without phenomenological reduction the specific phenomenological content of modalizations – in intentional acts – would be hard to explain. It would be impossible to understand why constant external factors (for instance, variations in the intensity of a stimulus) are accompanied by fluctuations in attention. It would also be impossible to understand the reasons why only the lived experience of causality – which I sharply distinguish from causality in the psychophysical sense of the term – transforms attention into a factor that allows the understanding of a situation by the subject who lives that experience. I claim at last that only the genetic analysis of Husserl’s late Freiburg period, with its distinction between primary and secondary attention, gives a full account of the relation between the thematic object, focused on an intentional attentive act, and the horizon that surrounds the object and gives it its ultimate meaning.