Ask me anything — the Logic edition

Is the following a valid logical argument?

1. Roses are flowers.
2. Some flowers fade rapidly.
3. Therefore, some roses fade rapidly.

Clearly it is logically invalid but it appears logical because it accords with our knowledge of the world — that some roses do fade rapidly.

The logical validity of a conclusion depends entirely on the premises, not on whether the world is some particular way. The statement “some roses fade rapidly” may be true in reality but it does not logically follow from the two premises, and therefore it is logically invalid.

OK, try this. Is this a valid logical argument?

1. Rolls-Royce cars are cars.
2. Some cars are cheap.
3. Therefore some Rolls-Royce cars are cheap.

This more clearly appears to be logically invalid because we know that RR cars are never cheap. But it’s the same argument as the roses argument. Both are equally logically invalid but one appeals more to our intuition than the other.

I bring this up because I wrote a piece in which I argued that our intuition about how the world works is usually wrong because our species evolved in a different sort of world. Check out this post — Our out-of-date Instincts — in the blog for the “How the world works” course.

This is an ask-me-anything post. So what’s on your mind?

6 thoughts on “Ask me anything — the Logic edition

  1. baransam1 Monday January 25, 2021 / 9:05 am

    I will like to know your thoughts on mental-depression.

    Being an economist, I have seen your extensive thoughts regarding poverty. But even for non-poor, life can be hell in spite of good food, good house, good clothes and good bank-balance. Science has prolonged the average human life and provided us with more free time. Maybe we have not yet figured out how to spend the additional time. Maybe that explains the many instances of depression around us.

    Your thoughts please.

    Like

  2. SanJay Srivastava Monday January 25, 2021 / 9:12 pm

    Hi Atanu,

    Would love to hear your thoughts about pros/cons of the Indian culture of accumulating gold. I did a rough back of the envelope calculation of the amount of capital in India tied up in gold and seems like a lot. My naive perspective is that it seems like a waste (maybe not from an individual’s perspective, but overall system)

    regards

    Like

  3. Mohan Boggara Tuesday January 26, 2021 / 12:49 am

    Hi Atanu,
    Hope you are doing well.

    Given the acceleration of digital technologies in all areas and especially evident in Covid situation, what do you envision the future of education in particular would be? Since the digital technologies allow a great level of partnership between the willing educators to create content and anyone willing to put in the discipline -(or at least be guided to follow a reasonable path-) to learn about any subject at any time, do you think the in-class eduction as we know will cease to exist? and what would that mean to the concept of school/university?

    Like

  4. Ajit R. Jadhav Wednesday January 27, 2021 / 7:12 am

    Quantum Mechanics.

    Best,
    –Ajit

    Like

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