Not everyone will believe in Karma, or more precisely, what people are confused with the nature's law of cause and effect (actions and the consequences of actions). Karma has become part of the superstitious belief in certain religions or cultures being limited and conditioned by the particular belief, values and practice about what is good or bad and right or wrong, however, the nature's law of cause and effect is not a belief, and it's nothing to do with the worldly thinking and belief about what is good or bad, right or wrong.
There are those who believe in everything is the act or the will of 'the creator of the universe', it's nothing to do with my actions and the consequences of my actions. It makes the minds feel better about themselves and everything, when they put the responsibility onto 'someone' else. It is fine, because everyone are free to have their own faiths and beliefs. One should respect that not everyone will believe in what one believes. One cannot force anyone to believe in something that they don’t believe in.
Although Karma is part of the belief or teachings in certain religion, or spirituality, or culture, while the nature's law of cause and effect, is nothing to do with belief or disbelief, it's just what and how things are, selflessly changing impermanently, influenced by the existing cause.
To know the Truth, it is not by reading books and philosophies, and it is not because the scriptures say so or our teacher says so. It should be coming from our own insight or direct experience towards seeing the Truth as it is, then it is the real Truth.
For example, maybe we don’t really know what will happen to us after the death of this physical body but we have heard from somewhere about Buddhas and Yogis – the enlightened Self, talked about the selfless reincarnation, more precisely, it's the restless selfless impermanent changes in the names and forms that are happening accordingly to different Karma (cause and effect) and intentions that we all had created for ourselves, either wittingly or unwittingly. Due to ignorance, there are many things that we don’t know, but we have had heard lots of different types of talking, or study, or discussion, about them. And we cannot say that it is true or untrue because we are ignorant towards the truth of it. We have to find out the Truth through our own practice of purifying, disciplining and quieting the mind, self-inquiry, meditation and self-realization, then we will know that whether something is true or untrue. Even though an enlightened being told us all about the Truth, we still have to find out by ourselves through self-inquiry and self-realization.
Yoga and Buddhism teach us about the law of cause and effect (actions and consequences of actions), which is the main force that is influencing our life, our personality, our desire, our actions and fruit of actions, and our worldly life experiences through our past accumulated boundless karma, or more precisely, boundless cause that is leading to effect, according to our previous intentions, desires, thoughts, actions and speech. And our present intentions, desires, thoughts, actions and speech will generate the cause (planting the seeds) that will determine our upcoming existence, personality and life experiences. Good and pleasant cause will bring good and pleasant experiences while bad and unpleasant cause will bring bad and unpleasant experiences.
From the surface, it seems like we are not free because we are bound by this law of Karma. But it is not really like that. It is because it is our own self that is creating the Karma (planting the seeds) for ourselves. If we do good, we will create good Karma. If we do bad, we will create bad Karma. According to the worldly religious/spiritual/cultural belief, values and practice, if we want to have good life and happiness in life, we can actually work on our intentions, desires, thoughts, actions and speech to create the type of life and experiences that we want. And what everyone think and believe what is good and bad, might be very different from one another. And hence, it's not accurate to judge that this is good karma or that is bad karma.
While the Yoga and Buddhism teachings do not stop at this level.
They teach us how to transcend both good and bad Karma (the perception of goodness and badness, positiveness and negativeness, pleasantness and unpleasantness) through the realization of selflessness, through mind purification to remove the veil of ignorance and impurities, the annihilation of the idea of 'I' and egoism, and renouncing from the fruit of actions.
More importantly is that in the many different thinking and beliefs in the world about what is good and bad, right and wrong, can be very different from one another. And hence, it's not about what the minds think and believe is good and right actions based on their particular thinking and belief, will bring pleasant and desirable consequences (pleasantness) in return, or what the minds think and believe is bad and wrong actions, will bring unpleasant and undesirable consequences (unpleasantness) in return.
Meanwhile many people like to use the word 'Karma' to threaten other people, as well as to be the excuse for oneself to inflict 'punishment' or 'abuse' onto other people out of one's desire, lust, anger and disagreement. "I am acting on behalf of 'the authority of the universe' or 'the creator of the universe' to punish you for your bad and wrongful behavior. You deserve some punishment because of your bad Karma (sin) for not obeying my wish, going against my desire, disagreeing with me, offending and disrespecting me."
Yoga and Buddhism teach us to go beyond good and bad Karma, to be detached from the perception of duality, and to go beyond all the different qualities of names and forms that are selfless and impermanent. They teach us that we don’t need to runaway from suffering or chasing after happiness and pleasurable enjoyment. They teach us to go beyond suffering and happiness/pleasurable enjoyment, be free from attachment, identification and the desire of craving and aversion, to uncover the unconditional peace beyond the pleasant and unpleasant states of the mind, or realizing selflessness of eternal bliss, unlimited wisdom and unconditional existence.
The minds that realized selflessness and impermanence, are not being determined or affected by Karma, cause and effect, or actions and the fruit of actions. That is real freedom, being undisturbed by pleasantness and unpleasantness, or desirable and undesirable experiences. It doesn't mean that one will have no self-control to be doing all kinds of actions that would hurt oneself and others and the surrounding environment, deliberately or randomly. One is performing actions that would bring benefits to oneself, others and the surrounding environment, but without craving towards the fruit of actions have to be something good, desirable and pleasant. One is not performing actions that would hurt oneself, others or the surrounding environment, without aversion towards the fruit of actions is something bad, undesirable and unpleasant.
May we all transcend duality, go beyond both good and bad Karma, or transcending the nature's law of cause and effect, be free from ignorance and egoism, and be really free.