The Three Marks of Existence in Buddhism
The three signs of Buddhism are anatta, dhukka, and anicca.
Anatta means “non-self” and is based on Buddhist ideas of codependent origination. Since the self is constituted by relations rather as an essence, the self is an illusion of autonomy. In actuality, the self does not exist separate from others. Because all origination is relational (there is no transcendent “essence”), everything is inherently empty. Emptiness, however, it is not meant to be read as “not existing.” Rather, it is the realization that all objects are empty of essences since their very existence is dependent on them being in relation to other objects. In a reality with infinite inputs, nothing can be claimed to originate from itself. Nagarjuna talks directly about this, denying that svabhava (a being for itself) is possible since nothing can create itself in a vacuum and transcends the relations with which produced it.
Dhukka denotes suffering. Suffering is a general theme in Buddhism, since we all suffer in conventional reality. We are suffering for three major reasons – (I) Our physical form creates pain through natural process such as old age, death, and sickness. (II) We are forced to make choices and therefore are also forced to eliminate certain outcomes, despite not knowing what those entirely might consist of. In other words, our limited knowledge creates suffering just by its very being. And finally, (III) we suffering because of impermanence (anicca). Because everything is in constant flux, always changing, we are unable to ground ourselves firmly in one unchanging reality. Thus, the inability to control annica stands at the heart of our suffering.
Annica signifies the concept of impermanence. Since everything is in motion, you will never experience the same phenomena twice. To give an example – if you walk alongside a river for two days, the first day of your experience will fundamentally be constituted differently than your second day. Impermanence thus admits to the flow of conventional reality and is the justification for Anatta.

A scroll art piece of Bodhidharma by Hakuin Ekaku (1686 to 1769). The letters read “Zen points directly to the human heart, see into your nature and become Buddha.”
The evidence for these three signs of Buddhism are persuasive. The case for Anatta is found in the evidence for codependent origination. It is certainly true that there are an infinite amount of inputs for any given being. Since all beings exist temporally, they must also exist relationally, not just to time but to other objects with which it is compared to. The function of an object, or the concept of self, is always relational since it cannot be derived on its own. Since there is no inherent essence, Buddhism through the concept of Anatta allows for a philosophy of “one-ness” that connects all beings in a great chain of codependent origination. The case for Dhukka comes from the realization that nothing material is inherently satisfying and that these pleasures are always trapped temporally and never transcendent. Because we are unable to ground ourselves in a fully recognizable reality, one which is constantly changing, we are constantly displaced which is the root of suffering. Finally, the case for Annica is multifold. One the one hand, meditation and the studying of nature itself will bring about the realization of impermanence. If all is relational (which we established with codependent origination), then it also follows that everything is constantly in flux. Because things do not exist by themselves alone, they are constantly rearranging the space from which things spring. It is because of this fact that Annica is reality. Alternatively, from a scientific standpoint, quantum mechanics have proved to us the capacity of “random” events on a sub-atomic level, constantly in motion due to probability. Therefore, quantum mechanics offers a compelling reason to believe impermanence is an accurate depiction of our actual-existing reality.
All of this claims are plausible since they are evidential by being derived from observable phenomena and meditative practice. That is not to say, however, that objections cannot be made. Dhukka condemns man to constantly view himself through the lens of suffering. The evidence for Dhukka is also difficult to grasp since there is virtually always room for something to be “better” than it is now. If one is not in a perfect situation (a situation which is arguably impossible), there is always room for improvement and thus there is always room for suffering. Since we are doomed to potentiality, we are also doomed to suffering. Anatta is problematic is some respects too, mostly because of its relation to codependent origination. Existentialists, among others, would argue that this is a type of determinism that negates individual agency. If all things exist purely relationally, and there is no essence, then there is no self-autonomy. However, I don’t take this position. Instead, I find the Buddhist conception of Anatta to be empowering since it places our existence in perspective of everything around us.
Everything truly is one great chain of relations.