In everything around us we see that there are instructions that govern the way things operate. The computer you are sitting at has instructions that it follows. The human body is instructed by genetics that govern very specifically the way we are physically structured and function. The laws of physics act as instructions governing the way matter operates. An example of this is gravity that exists all throughout the universe holding things in their place. Even at the atomic level, the basic elements interact with each other in a specific manner. Everything is governed by instructions or laws that keep things structured and in order.
Upon entry into this world, the mind of a newborn baby is essentially like a blank slate. It lacks much of the instructions it needs to function. Mentally speaking, as a person grows and learns, they become a product of their environment. The things they are told and the things they see (whether good or bad, true or false) become the instructions for that persons mind. When a mind is young it's like a sponge soaking up as much information as it can get. The environment in which that mind develops will largely determine the direction and beliefs of the individual, so it is only natural to want our minds to be filled with as much beneficial and truthful knowledge as possible and as little error or destructive information as possible.
Deception and error aren't always obvious. There are plenty of examples in history where people and even masses of people are led into error. In 1943, 100,000 young people in brown shirts filled the Olympic stadium in Munich Germany. They formed with their bodies a sign for a fanatical, yet persuasive man standing behind the podium. The message read "Hitler, we are yours." Their environment and upbringing resulted in the destruction of Europe and the slaughtering of innocent millions. Years later, a group of Chinese students were persuaded to read and memorize the sayings of a little red book, "The sayings of Chairman Mao". The result was a cultural revolution that still keeps a billion people under the slavery of communism. It's easy to see how vulnerable people are to their surroundings.
One of the most dangerous aspects about an error or a lie is it's ability to spread around like a flu virus. After a lie, culture, or a behavior is introduced and has spread to several million people over the course of time it becomes far more credible because subconsciously, many people mistakenly believe that "millions of people cannot be wrong". The "go along with crowd mentality" comes into play because people feel safety in numbers. People tend to conform to those around them and become like one another. Another tremendous problem lies in the fact that people are a mixture of truth, error, ignorance, and imagination. Since humans are social creatures, they pass on what they have seen, heard, and believed and this is oftentimes compromised by errors. Human beings have a bad habit of corrupting people around them without even realizing it. There are quite a few factors in society that contribute to this; Greed, ignorance, power, materialism, selfishness, human error, immaturity, egotism, pride, emotions, and other human characteristics. All of these factors are a product of an imperfect human mind that can pervert, water down, or obscure the truth. They help produce the opposite of truth which is falsehood and error. When the truth is compromised it affects all of us.
How can a person know that their minds are not the product of bad information or a corrupted culture being spread around like a virus? All too often we sell ourselves short. Sometimes it behooves us to question and ask ourselves why we believe and do the things we do. Our minds, as complex as they are, cannot always be trusted. Feelings can't always be trusted. They change like the weather. One moment you can be happy, the next, you're sad. Science is often found to be mistaken when knowledge advances and theories are proven wrong. The more knowledge we become aware of, the more we realize how little we know. Without all the pieces of the puzzle in place, it's impossible to draw a conclusion that is 100% certain, yet as humans, there is not a person alive who possesses all knowledge or all the pieces of the puzzle. Most of us don't even come close to it. This brings me to my final point.
There is truth regarding absolutely everything. There is not a situation that exists or that can be imagined where there is not a truth or set of truths pertaining to it, despite the fact that an individual may be unaware of them. We either know what is true, we know what is false, or we don't know enough of the facts to be certain. Many people believe that the truth is relative and that there's no such thing as absolute truth. This is an unfortunate mistake. Relativity is the result of the limited amount of knowledge and capacity of the human mind, but the truth is not limited to the human mind's ability to perceive or qualify it. Believing in something does not necessarily make it true, and not believing in something doesn't always mean it's false. For example, many children believe that Santa Clause rides around in the sky being pulled by a herd of reindeer. No matter how sincerely these children believe this, it has no effect on the reality that it simply isn't so. The same applies in negative sense as well. If I didn't believe that the earth revolved around the sun, no matter how sincerely I held that belief to true, I'd still be very wrong. Therefore we see that truth is not dependent on a human mind to make it truth and Perception is not always correct. This is why the truth is not relative. Human beings are notorious for making mistakes and being wrong. Sadly many people are mistaken in their beliefs. If I say there is one God, and Jane Doe says there are multiple gods, and Joe Blow says there is no such thing at all, simple logic tells us that two of the individuals are wrong and one of them is correct. We know this because it's a logical impossibility for an object, person, or thing to exist and not exist at the same time. Thus we see it's only logical that truth exists entirely outside of an individual and is not relative. People tend to look inward to their own imperfect selves for answers, when in fact they should be searching for the truth outside of themselves. There is absolute truth regarding everything. Your job is to find it. Truth is very real, very tangible and you will know when you have found it.