According to Humes's argument, induction by its nature assumes a uniformity that is not justified.
Uniformity isn't necessarily assumed, but it is inferred if the data coming in is consistent enough. The 'white swan' example only works because all swans from 1 to n are white. What colour is a tulip? The data will indicate whether an assumption of uniformity is rational or not.
It's the same with the uniformity of laws of physics - to the best of our ability to observe, the fundamental rules that we've discovered seem to apply universally and with an amazing degree of accuracy. Models where the laws of physics are mutable, while interesting, don't describe the universe we find ourselves in nearly as well. We didn't take uniformity as a starting assumption (indeed the opposite - 'celestial' and 'terrestrial' physics were once believed to be categorically different), rather a conclusion from repeated observation.
This is a very deep and interesting observation...
To paraphrase said observation: "Things that seem consistent/uniform may not in fact be consistent/uniform"
Indeed! It's been the relentless search for abnormalities and investigations into such that drives most of our scientific endeavours! See the discovery of the atomic nucleus for a dramatic disproof of the uniformity of goddamn solid matter itself!
However, I have a feeling this is a prelude to some religions apologetics, and religious apologists aren't thinking about things like that, right? Sure enough:
... and a point often used by the religious to justify that any observation reached using scientific method uses induction, and therefore is purely speculative, and likely irrational.
... Because tentatively adopting a conclusion supported by the data we have so far and willingness to change views in the face of new/better data is EXACTLY like pure speculation?
- Scientific inquiry shows us that there are far more stars in the sky than can be seen with the naked eye, that many of those stars have planets and that there are whole categories of weird things out there in space that we couldn't have even guessed at only a few hundred years ago. This is EXACTLY as valid as speculating that God's janitor, Barry, goes out each night to hang the stars one-by-one on a big velvet curtain over our heads?
- Scientific inquiry has brought us the tools we rely on to diagnose and treat diseases far better than at any point in our history, greatly contributing to the unprecedented quality and duration of our lives. Microbiologists can even show us pictures of the pathogens that make us sick, and toy companies can turn those pictures into cute plushies. This is EXACTLY as valid as speculating that illness is brought on by demons, imbalance of humours, bad fung-shui or curses by witches?
- Scientific inquiry has unearthed a fascinating story of the planet we live on, of how plate tectonics floating on a molten mantle change the face of the planet over unfathomable timescales; of the ever-changing forms of life populating the land, sea and air; of wild changes in climate and of catastrophic mass-extinction events. This is EXACTLY the same as speculating that we live on a 10,000-year-old, four-cornered flat earth resting under a dome held aloft by pillars at the world's edge?
So while everything we know through science may be wrong in the sense of not being 100% correct, we know that we're less wrong today than we were yesterday. I wrote a lengthier response addressing this in the 'Fallibilism' thread.
Is a conclusion based on induction rational or irrational? Does it always work?
Yes and no, respectively (and depending on what you mean by 'work').
It is entirely rational to hold a conclusion to be tentatively true based on the weight of evidence to date. Let's go back to the swans for a moment and try a slight variation (literally) with a combination of induction and deduction:
- All swans I have seen so far are white.
- Genetic variation, mutation and other extremely well-established principles of biology can trivially introduce changes in pigmentation.
- It is not rational to conclude that all swans must be white. (Though I can rationally posit that most are if my sample size warrants)
Remember that science isn't some stamp-collection of facts, it's an interconnected web of facts, theories, experiments, etc. If we are using induction and arriving at wrong conclusions, we can usually remedy our error by including more data - either by going out to find it or by considering sources we may have neglected at first.
Not all swans are white, but are all heavenly bodies bigger than asteroids - that is: rocky planets, moons of sufficient size, gas giants, stars, etc. - (roughly) spherical?
- All naturally-occurring heavenly bodies above a certain size threshold observed so far are (roughly) spherical
- There are known mechanisms (gravity, etc) that explain the shape and slight deviations and why there is a size threshold and why other shapes would be unstable
- It is rational to conclude that all naturally-occurring heavenly bodies are roughly spherical
Is deduction rational or irrational? Does it always work? ( assuming something can be rational always works, which may or may not be the case)
As others have pointed out, if the rules of logic are followed properly then yes the deduction is rational. If the premises are correct you'll get the added bonus that the conclusion will be correct. Depending on your definition of 'work' that'll translate to a 'yes' or a 'no'.
Can the conclusion that there is a creator of the universe be rational?
A very heavily qualified, theoretical 'yes'. IF valid premises lead to the logical conclusion, yes. HOWEVER: my assessment of the facts, as well as that done by many extremely knowledgeable people, have come to the conclusion that the universe we happen to find ourselves in does not support any of the premises required to arrive at a conclusion that our universe was created by some outside entity, much less that there's a cosmic being out there that has any concern for our little blue-green planet or the creatures thereon.
So when you ask:
Also please watch this. Is the logical proof for god valid?
I will refer you to this excellent index of creationist claims.
Hamza (person in the video) makes the argument that we can make a logical conclusion that a person is likely to have a great great great great grandparent. But isn't that assumption purely based on the evidence of his own existence, and thus induction?
Again, there's a whole body of knowledge that we've built through repeated observation, experiment, rigorous testing, etc. over the last few hundred years.
Induction is a powerful tool when you combine multiple lines of evidence into a succinct but powerful and predictive conclusion. Remember, though, the lesson of the black swan - all conclusions should be held tentatively, not absolutely.
However, the more we learn the closer our conclusions come to the truth. A black swan goes against our hypothetical notion that all swans are white, but at least there is a mechanism where we could accept - even predict - that an outlier would be found. Some claims, however, violate multiple well-supported lines of evidence. We would be foolish to accept a claim that Hamza sprang full-formed from the split skull of his father, violating everything we know about physics and biology, without an exceptionally comprehensive body of supporting evidence to back the claim!