When yogis comprehend mind and matter arising and disappearing at every moment, then they will come to comprehend the impermanence of the processes of lifting the foot, and they will also comprehend the impermanence of the awareness of that lifting. The occurrence of disappearing after arising is a mark or characteristic by which we understand that something is impermanent. If we want to determine whether something is impermanent or permanent, we must try to see, through the power of meditation, whether or not that thing is subject to the process of coming into being and then disappearing. If our meditation is powerful enough to enable us to see the arising and disappearing of phenomena, then we can decide that the phenomena observed are impermanent. In this way, yogis observe that there is the lifting movement and awareness of that movement, and then that sequence disappears, giving way to the pushing forward movement and the awareness of pushing forward. These movements simply arise and disappear, arise and disappear, and this process yogis can comprehend by themselves — they do not have to accept this on trust from any external authority, nor do they have to believe in the report of another person.
When yogis comprehend that mind and matter arise and disappear, they understand that mind and matter are impermanent. When they see that they are impermanent, they next understand that they are unsatisfactory because they are always oppressed by constant arising and disappearing. After comprehending impermanence and the unsatisfactory nature of things, they observe that there can be no mastery over these things; that is, yogis realize that there is no self or soul within that can order them to be permanent. Things just arise and disappear according to natural law. By comprehending this, yogis comprehend the third characteristic of conditioned phenomena, the characteristic of anattā, the characteristic that things have no self. One of the meanings of anattā is no mastery — meaning that nothing, no entity, no soul, no power, has mastery over the nature of things. Thus, by this time, yogis have comprehended the three characteristics of all conditioned phenomena: impermanence, suffering, and the non-self nature of things — in Pāli, anicca, dukkha, and anattā.
Yogis can comprehend these three characteristics by observing closely the mere lifting of the foot and the awareness of the lifting of the foot. By paying close attention to the movements, they see things arising and disappearing, and consequently they see for themselves the impermanent, unsatisfactory, and non-self nature of all conditioned phenomena.