Valid arguments vs. sound arguments

Validity and soundness are one of the most important terms in logic. How to distinguish between deductively valid and invalid arguments as well as between sound and unsound arguments? The definition is very much straightforward and it is all that is needed to grasp the idea. However, this post will also give you a brief description of a few examples which will provide you with a more practical approach to the problem. And at the end of the post I will reveal to you a little secret which will turn this logical issue into a piece of cake!

Valid argument means an argument whose conclusion cannot be false if its premises are true. Consider the following example:

5 invalid arguments that God does not exist

We have already dealt with some logical fallacies and you know how to classify them. Logical fallacies are often used in advertisement and politics but are even more explicit when it comes to religious debates. “Does God exist?” is one of the oldest philosophical questions, and to many the most important one. You have probably heard at least one argument starting with: “If God exists, then why…” or “If God is A, then why does B happen?”. It should be made clear that a huge number of these arguments are invalid and should be classified as logical fallacies. Nevertheless those who are not familiar with rules of constructing valid arguments (what is validity?) may not notice that many arguments against God’s existence are flawed and may even find them quite convincing. If you want to know what the most popular invalid arguments and their flaws are, here is the list of 5 false arguments stating that God does not exist with a brief explanation of their flaws. Some of these arguments refer strictly to the Christian God and are therefore explained in terms of Christianity.

Philosophy: Brain in a vat argument – truth revealed

Brains in a vat… That sounds terrifying, doesn’t it? Brain in a vat argument is one of the newest thought experiments in philosophy of mind (discussed by John Pollock). Many people raise objection to the brain in a vat theory but are there in fact any arguments against brain in a vat? Can you argue against it? Brains in a vat are used to support sceptical perception of the world and solipsism theory. You should know that this argument is not a real novum. A brain in a vat problem bears a striking resemblance to older theories such as the dream argument by Zhuangzi.

But what is brain in a vat? Imagine an evil scientist whose advanced knowledge enables him to remove your brain and put it in a vat with all nutrients which are necessary to maintain the organ alive. Before your brain was removed it had been receiving electrical signals via neurons in your body. Now it is placed in a vat in the evil scientist’s laboratory and receives signals by electrical stimulation coming from a laboratory computer…

Logical fallacies classification - formal and informal fallacies

Logical fallacies are classified in many different ways since there is still no agreement between thinkers for that matter. What are logical fallacies? The best definition of a fallacy in logic is an argument with poor reasoning (critical thinking rules can easily unmask flawed conclusions). The most basic classification divides logical fallacies into two main groups – formal fallacies and informal fallacies.

Formal fallacy simply describes an error in a logical form of an argument. One of the most common formal fallacies is known as proof by example. It occurs when the speaker (or writer) uses an example to make overgeneralisations (this fallacy is often used in propaganda). Consider the following example:

Logical fallacies examples – appeal to novelty and age

As always let's begin with a simple definition. A logical fallacy is an error in reasoning which usually relies on a wrong assumption made in the argument. Appeal to emotion is one of the most popular types of logical fallacies – examples of these fallacies may be very often found in the advertisement. Today I would like to describe you two very popular fallacies relying on appeal to emotion – argumentum ad novitatem and argumentum ad antiquitatem. You will be surprised how often we are unaware of these reasoning tricks. You may ask – why should I care about the fallacies at all? Well, developing your critical thinking skills is necessary not only if you want to succeed in philosophy but practically in (well, almost) every profession. It's very likely that while arguing you have used these fallacies yourself without even noticing them.