Can Logic Alone Lead Us to Truth?

Written by: Tushar Sharma

If you’ve lived all your life on Earth—just like the rest of us—you'd probably say it’s the elephant. Why? You may never have done the experiment yourself, but it seems logical. But here's a deeper question: Can we rely solely on logic to lead us to truth?

Now imagine you had special powers and lived on the Moon instead. In that case, you might answer differently. On the Moon, with no atmosphere to create air resistance, a feather and an elephant would fall at the same time. This isn’t just theoretical—NASA astronauts during the Apollo 15 mission actually performed this experiment using a hammer and a feather. The results were clear: both objects hit the lunar surface simultaneously.

So why don’t they fall at the same rate on Earth?

It's because of air resistance. Earth has an atmosphere, and as objects fall, they experience drag depending on their shape, mass, and surface area. A feather flutters down slowly due to its large surface area and low mass, while an elephant plummets quickly.

But let’s look at what physics tells us about gravity:

According to Newton's Second Law, force equals mass times acceleration:

$$ F = m \cdot a $$

And the gravitational force between two objects is given by Newton's Law of Universal Gravitation:

$$ F = G \frac{m_1 \cdot m_2}{r^2} $$

If we equate these two expressions (since gravity is the force acting), and let $ m_1 $ be the mass of the falling object:

$$ m_1 \cdot a = G \frac{m_1 \cdot m_2}{r^2} $$

We can cancel $ m_1 $ from both sides:

$$ a = G \frac{m_2}{r^2} $$

This shows that the acceleration due to gravity does not depend on the mass of the falling object—only on the mass of the planet and the distance from its center. So in a vacuum, all objects fall at the same rate regardless of their mass.

But What About Logic?

Let’s consider a few more examples where logic alone might mislead us:

“There must be a god because the universe is so perfectly tuned.”

This argument relies on what’s known as the design fallacy. While the physical constants of the universe do appear finely tuned for life, this observation doesn’t prove the existence of a divine designer. It may be true, or there could be other explanations such as multiverse theory or unknown natural laws. Without empirical evidence, logic alone cannot confirm such claims.

“The Sun orbits the Earth—it looks like it moves across the sky!”

Before Copernicus and Galileo, this seemed perfectly logical based on observation. After all, the Sun appears to rise and set. But appearances can be deceiving. We often accept scientific facts on trust—like many people today believe the Earth orbits the Sun simply because their science teacher said so, without ever having conducted the experiments themselves.

“If something feels morally right, it must be right.”

Morality is deeply tied to culture, upbringing, and personal belief. Consider how slavery was once considered "natural" and even morally justified by many societies. Over time, increased awareness, empathy, and understanding of human rights led to a shift in moral thinking. This evolution shows that morality is not fixed logic, but a dynamic process informed by experience and evidence.

“Light must be a particle since it scatters through a prism.”

Newton believed light was made of particles, partly based on his prism experiments showing how white light splits into colors. However, later discoveries like the double-slit experiment showed wave-like behavior, and Einstein’s explanation of the photoelectric effect brought back the idea of particles. Light turned out to be both a wave and a particle—a concept only revealed through experimentation and further refinement of theory.

When Logic Isn't Enough

There are countless theories throughout history that seemed logical at the time, yet were proven wrong by empirical evidence:

Miasma Theory: The belief that diseases were caused by "bad air."
Steady State Theory: The idea that the universe has always existed in an unchanging state.
Geocentric Model: The belief that Earth is the center of the universe.
Spontaneous Generation: The idea that life can arise from non-living matter.

These theories were eventually replaced not because they lacked logic, but because they failed under experimental scrutiny.

“The test of all knowledge is experiment” — Richard Feynman

Logic is a powerful tool—it helps us form hypotheses, ask questions, and make predictions. But truth ultimately lies in the real world, and the only way to access it reliably is through empirical testing. The universe doesn’t care how logical our reasoning seems; it reveals itself only when we test our ideas against reality.