Euclidiana Get the app
LSAT Logic Prep for iPhone

Read arguments the way a logician does.

The LSAT rewards one skill above all: turning ordinary prose into formal structure. Euclidiana trains exactly that — logical reasoning questions are explained in formal notation, with named inference rules and diagrams where the logic calls for them.

Download on the App Store

Free to download · 7-day free trial · $19.99/month or $99.99/year after

Euclidiana app — LSAT logical reasoning practice

Narrative in. Logic out.

Most prep apps tell you which answer was right. Euclidiana teaches you the argument's formal structure — a discipline of translating language into formal logic, the method behind the app's pending patent.

1

Isolate the claims

Each stimulus is broken into its premises and conclusion, with the logical trigger words — "only if," "unless," "precisely what produces" — surfaced and color-coded so the argument's skeleton is visible.

2

Translate to symbols

Plain English becomes formal notation: a variable legend maps each concept to a symbol, and the argument is rewritten as conditionals, biconditionals, and negations you can actually check.

3

Name the move

Every explanation names the exact inference rule or fallacy at work — modus tollens, affirming the consequent, a dropped scope condition — so you recognize the same pattern on test day.

Formal notation, not paraphrase

Logical reasoning explanations use real notation — →, ↔, ¬, ∴ — with a legend for each variable. You see why the right answer follows and where each wrong answer breaks the chain.

Diagrams that show the logic

Conditional questions render as nested sets; causal questions draw the claimed arrow against the confounder the argument ignored. Abstract structure, made visible.

Weak spots become drills

Miss a question and the app isolates the exact construct you fumbled — post hoc, sampling, equivocation — and drills it until you hit a three-in-a-row streak.

Inside the app.

Six screens, no ads, no streak nags. A question, a clock, and the explanation that shows you the structure underneath.

  • Euclidiana home screen showing the Mastery Collection and weekly progress

    Ten reasoning constructs, filling in as you drill.

  • A timed logical reasoning question with five answer choices

    Authentic stimuli, five choices, LSAT clock.

  • A revealed answer with colour-coded stimulus, formal logic translation and a Venn diagram

    Colour-coded structure, formal translation, diagram.

  • A mastery drill on the post hoc fallacy

    Miss one, and the flaw becomes its own drill.

  • A Quant Gym arithmetic question

    Quant Gym — arithmetic, algebra, data, comparison.

  • A performance screen with an accuracy trend chart and per-construct accuracy bars

    Accuracy week over week, broken out by construct.

326

original questions — timed logical reasoning forms plus a Quant Gym warm-up that primes quantitative reasoning before test day

7

days free in the iPhone app — try every form, drill, and explanation with a full free trial, no commitment

0

ads, streak nags, or gimmicks — just the argument, the clock, and the explanation

★★★★★

“I'm shocked”

I can't remember how I found this app but I'm amazed at how much it has helped. I can see them competing with the big names. I was a skeptic at first but I don't mind paying anymore as I prepare for the November LSAT. The plain English explanations is some of the best I've seen, I feel more confident….
LawHER94 · Aug 26 · App Store review

Judge the explanations before you download.

This is one real question from the bank, already answered, exactly as the app shows it once you commit to a choice — colour-coded structure, the revealed key, and the explanation that names the flaw.

Necessary · Easy · Sample — answer revealed

Astrobiologists have established as a foundational principle that liquid water is necessary for life as currently understood, because every biochemical process essential to metabolism requires an aqueous medium. The Kepler Space Telescope has confirmed that Planet Kepler-22b has liquid water present on its surface based on spectroscopic and thermal data. NASA researchers therefore conclude that Planet Kepler-22b harbors life.

The NASA researchers' conclusion is flawed because the argument

  1. relies on circular reasoning — the definition of life already presupposes the presence of water
  2. commits valid reverse-negation application of the rule incorrectly by deriving a negative conclusion from a negative premise
  3. treats one sufficient condition as the only route to the outcome by inferring the absence of life from the absence of water in a related case
  4. treats a necessary condition for life as though it were a sufficient condition, inferring the presence of life from the presence of what life merely requires — Correct answer
  5. makes an unsupported empirical assumption about the generalizability of Earth-based biochemistry

Explanation

Life → Water (water is necessary for life). The planet has Water. The argument infers Life — treating the necessary condition as sufficient. Water is required for life, but does not guarantee it.

Start your 7-day free trial on iPhone.

Every question, every explanation, free for a week in the app. If the method earns your trust, it's $19.99 a month or $99.99 a year.

Download on the App Store

Questions? Djwinarick@gmail.com