The Buddha rejected the view that everything is the result of karma on several occasions. In one such instance the wanderer Sivaka asks the Buddha about this:

“Master Gautama, there are some ascetics and brahmins who hold such a doctrine and view as this: ‘Whatever a person experiences, whether it be pleasant or painful or neither-painful-nor-pleasant, all that is caused by what was done in the past.’ What does Master Gautama say about this?”

“Some feelings, Sivaka, arise here originating from bile disorders: that some feelings arise here originating from bile disorders one can know for oneself, and that is considered to be true in the world. Now when those ascetics and brahmins hold such a doctrine and view as this, ‘Whatever a person experiences, whether it be pleasant or painful or neither-painful-nor-pleasant, all that is caused by what was done in the past,’ they overshoot what one knows by oneself and they overshoot what is considered to be true in the world. Therefore I say that this is wrong on the part of those ascetics and brahmins.

“Some feelings, Sivaka, arise here originating from phlegm disorders … originating from wind disorders … originating from an imbalance [of the three] … produced by change in climate … produced by careless behavior … caused by assault … produced as the result of karma: how some feelings arise here produced as the result of karma one can know for oneself, and that is considered to be true in the world. Now when those ascetics and brahmins hold such a doctrine and view as this, Whatever a person experiences, whether it be pleasant or painful or neither-painful-nor-pleasant, all that is caused by what was done in the past,’ they overshoot what one knows by oneself and they overshoot what is considered to be true in the world. Therefore I say that this is wrong on the part of those ascetics and brahmins.” (Bodhi 2000, pp. 1278-1279)

In his reply to Sivaka, the Buddha asserts a variety of other causes and conditions besides karma that contribute to what is experienced in the present. In his book, Exploring Karma & Rebirth, Nagapriya explains the later analysis of this discourse in the commentarial tradition and how it places karma in the larger context of several different types of causality:

“While the schema outlined in the Moliyasivaka Sutta is a bit obscure, Buddhist scholastic philosophy (known as Abhidhamma) classified five modes – technically known as niyamas – of dependent origination. These modes are (1) physical inorganic (utu-niyama), (2) biological (bija-niyama), (3) non-volitional mental (mano- or cittaniyama), (4) ethical (kamma- or karma-niyama), and (5) spiritual (dhamma- or dharma-niyama).

“Examination of these niyamas can give us a better understanding of the scope and importance of Karma in human life. The utu-niyama embraces natural laws such as those of physics and chemistry. For example, when seeking an explanation for the occurrence of an earthquake we may be served better by the theory of plate tectonics than by the theory of Karma. The bija -niyama governs the physical organic order, including the laws of biology. For example, if I catch a cold it would seem more sensible to explain this by supposing the presence of a virus rather than by supposing ‘moral’ causes. The mano- or citta-niyama governs the laws of the mind and to some extent relates to psychology. The phenomenon of shock or post-traumatic stress may, for example, be best explained under this heading. The karma-niyama governs the sphere of volitional human conduct (including body, speech, and mind). In practice, it does not seem easy to separate the non-volitional and volitional mental spheres. The exact meaning of dharma-niyama and what it governs is not clear. A traditional account links it to miraculous events in the Buddha’s life, but it can also be thought of as the principle that underlies spiritual evolution. Seen in this way, the dharma-niyama explains the process by which we can transcend our selfishness, hatred, and ignorance and achieve generosity, compassion, and understanding. In traditional terms, it explains how it is that we can break free from the determining influence of Karma and rebirth and so put a stop on the wheel of perpetual re-becoming. It underlies the dynamics of spiritual development.

“A further way of thinking about the dharma-niyama is to see it as the ‘undeserved’ compassionate influence that someone may exert on our life. In other words, it is the impact of the saint on the world. The saint does not act towards others in accordance with their karma but deals compassionately with everyone, regardless of merit. (Nagapriya, pp. 36-38)

The Buddha’s general theory of dependent origination is as follows: “When this exists, that comes to be; with the arising of this, that arises. When this does not exist, that does not come to be; with the cessation of this, that ceases.” (Bodhi 2000, p. 575) This means that all things come to be only due to causes and conditions and have no inherent existence in and of themselves. These causes and conditions operate according to these five niyamas or categories of natural law, of which the law of karma is only one of the five, and all five interact with each other in order to bring about life as we experience it. As Nagapriya so eloquently explains:

“The five niyama analysis of experience shows that Karma is just one application of the general principle of dependent origination and, therefore, many circumstances and outcomes are likely to be governed by conditions only very indirectly related to Karma itself. But we should beware of seeing these different orders of conditionality as completely discrete. In reality, they are not five distinct orders of conditionality. This is only a map of what happens. Every experience comprises a vast network of conditions; our previous moral conduct will often have a bearing on our present experience, but in many situations non-moral factors may well exert a more decisive influence. The teaching of the five niyamas thus presents a more complex and subtle account of why things happen as they do than the crude view of Karma criticized above. We need also to remember that the actions of other people may be more decisive in any given situation that our own karmic stream; it may be their evil or their goodness that causes us to suffer or benefit, rather than our own.” (Nagapriya, p. 39)

Each situation we are faced with in life is brought about by many forces, in each present moment it us up to us to determine whether we will act in that situation in a wholesome or unwholesome way – mentally, verbally, and physically. We have the freedom to make a good cause or a bad cause in relation to whatever situation we are faced with. In each moment, our mental, verbal, and physical actions will change the way we relate to, interact with, and experience the situation for better or worse. The causes we freely make will also have an effect on the future, whether they come to fruition later in life or in some future life. While not all is determined by karma, karma is our own particular responsibility and a decisive factor in shaping the course of our lives.

Currently, the alternatives to the Buddhist teaching of karma and rebirth boil down to one of two views, the materialistic or the theistic. In the materialistic view, there is no necessary connection between the moral intentionality of actions and the way the lives of beings unfold. Furthermore, nothing of the psyche carries over past brain death since mind is only the epiphenomenon of the brain. The theistic view insists that everything that happens does so according to God’s plan, or because he wills it to happen, or at the very least allows it to happen. … [E]ither of these views denies the law of karma whereby one’s intentional actions (which is what “karma” means) is a determining or even decisive factor in how the lives of beings will unfold over time and over lifetimes. The Buddha claimed to have verified through his experience of recalling his own past lives as well as an extrasensory perception of the karmic unfolding of the lives of other beings that rebirth and the law of karma are realities and on that basis he refuted the materialists and theists of his day. He also repudiated those views by pointing out that the denial or misrepresentation of the law of karma undermines the motivation for morality and spiritual cultivation.

Materialists and theists counter that there is no proof that there is such a thing as rebirth or the law of karma. The testimony of the Buddha given in the sūtras that beings are reborn and that the quality of their lives is determined by the nature of their own actions is only valid if one accepts that testimony or if one is also able to verify it by experiencing past-life recall. On the other hand, the metaphysical views that there is nothing more than material interactions or that there is a God who created everything and is ultimately responsible for all that happens are also claims that cannot be proven or disproven, at least at this time. So, in terms of which belief is the most credible or makes the most sense – the materialistic, theistic, or karmic – that will have to be determined by each person for him or herself.